As far as I can tell that only happens when you have a space in the private key. No spaces between 5 and the rest of it either.
bob123's command should do the job.

Correct When you copy them make sure there are no spaces: The "Omit spaces in key data" checkbox will fix that for you.

Are you sure you imported a private key and not an address?
A base58 encoded private key starts with 5 while addresses only start with 1 or 3 in Armory.

Sorry for not getting back to you promptly on the other thread - volunteer support and all that.
For Electrum you need to input the line that starts with PrivBase58 with no spaces (and don't include "PrivBase58:" itself).
Armory has an option to "Omit spaces in key data" which will make that easier.
Ideally just the one line that corresponds to the receive address you used.

If that works, Electrum should display your address and balance quickly after.

It'd take some time to rebuild after using that option, but if ArmoryDB has crashed before that I don't think it'd do much without a restart.
Close Armory. Go to %appdata%\Armory and delete just the databases folder. Start Armory. Does ArmoryDB.exe still crash?

You're also welcome to post your logs files (armorylog.txt and dbLog.txt) on somewhere like pastebin or 0bin and link them for us to view.
May need to split them if the files are too large.

Going on that error, I think you need KB2999226 installed for Electrum to run.
If we're going down the export/import route, can you tell me whether the address you sent the bitcoins to starts with a 1 or whether it starts with a 3?

Probably the Armory database folder that needs a wipe and rebuild. You were on 0.96 before?

Great - that'll be enough space at least.
As bob123 has mentioned above, you really just need to copy the address (that you sent the bitcoins to) into the search box on the explorer.
Once Bitcoin Core is up to date Armory will then need to process the data, which will take some time - not as long, but not fast either.

Again, as bob123 mentioned there are other, lightweight, wallets that don't require the entire bitcoin blockchain to be downloaded - there are pros and cons to either option but while Armory is excellent it is perhaps not the best choice for newbies and it can be finicky to get working for those unfamiliar with it.
Unless you chose a P2SH-P2PK address we can get your coins into another wallet reasonably easily. Up to you to decide, really.

First up, they're not lost - don't worry. Keep your Armory wallet files safe - keep your password for that and the seed words (paper backup) safe too. You can check the wallet address's balance on a blockchain explorer like blockchair.
1 year and 46 weeks to sync? Are you sure Bitcoin Core isn't saying it is a year and 46 weeks behind? Is your internet slow?
Do you have 190GB of free disk space? You'll need it for the full download of the Bitcoin blockchain.
Don't panic if the answers to these questions aren't great, just let us know and we can provide some advice on how you should proceed.

While you're waiting, make sure you have Armory 0.96.4

Armory relies upon Bitcoin Core for the transactions in the blockchain data. No data then no transactions or balances.

Hi,

Bitcoin Core needs to be fully synced before Armory will see those coins. As long as you have that Armory wallet, they're not lost - you can check this by going to a block explorer and inputting the address: https://blockchair.com/bitcoin/blocks
Make sure you are running Armory 0.96.4 - Older versions may fail to update properly.

It will take some time, yes. For reference blk01313.dat is the latest on my machine, at least. That log file is increasing past block #74, right?
I'm hoping this external drive is connected via USB3 or better - Might take an excruciatingly long time if it is USB2

"Bitcoin Install Dir" is where the binaries are and "Bitcoin Home Dir" is where the bitcoin blockchain has downloaded to. The latter will contain the blocks & chainstate directories (and more).

Going on your initial description above, I think you have it set up correctly.
Unfortunately allowing Armory to manage bitcoind/bitcoin core can be unreliable - tend to recommend running things manually, but this requires config files/cli args to be set up too.
Regardless of whether Armory is set to spin up Bitcoin Core for you, Armory has to maintain its own database and must read and index the blockchain itself to do so; depending on your machine's specs it could need to spend a while preparing the database and scanning for transactions. Initial scans take a while but Armory won't take very long to catch up if you are a few days out of date.

There will be several log files in /home/user/.armory/ (unless linux handles it differently) that you'll want to check to make sure Armory is actually doing something useful.  dbLog.txt should have some entries that end with "parsed block file #N", but an increasing integer instead of N. armorylog.txt is important too.
Those two logs are those most commonly asked for when troubleshooting - you're welcome to post them to pastebin or another similar service if you need some help.

Step 1: Don't use bitcoinarmory.com

https://btcarmory.com/ or https://github.com/goatpig/BitcoinArmory/releases
You probably want armory_0.96.4_amd64_gcc4.7_noasm.deb
On Stretch, you'll need a bunch of qt4 dependencies too.

"in the long?"... Don't bank on any further official support for BCH in Armory. Goatpig is unlikely to fix it if/when any hardforks break BCH usage - as I understand it, it has been provided as a courtesy to get the coins out, nothing more. If it does break on the 15th, you're probably limited to exporting keys at that point or forking Armory and fixing it yourself.

Hopefully just Bitcoin Core itself that is running behind, but Armory needs that data. Close Armory down and start up Bitcoin Core. Go to Help -> Debug Window -> Information.
Look for the figure next to "Current number of blocks". More or less than 510893?

Block #510893 was mined back in late February, so you're not going to see any transactions since then. If that number isn't going up at all, something is wrong with Bitcoin Core's sync.

Going to wager that your cpu is reasonably old.
Pretty sure you need armory_0.96.4_amd64_gcc4.7_noasm.deb from https://github.com/goatpig/BitcoinArmory/releases/tag/v0.96.4
Also labeled Armory 0.96.4 Ubuntu/Debian 64-bit with GCC 4.7 on the main site's download page.

https://cyber.bgu.ac.il//advanced-cyber/airgap
There are a couple of videos on the page above, but this is the direct link to the "BeatCoin" paper's pdf.

I've seen exploits of this nature in the past but this one can use the GPIO pins on a raspberry pi to transmit the data (see first video). Given that historically Armory has offered downloads for the raspberry pi, and many here use the split online-offline/cold storage setup, I've posted here for awareness/discussion. Relevant to more typical computers/laptops too.

This all assumes the offline machine has been compromised. While we can minimise the chances of that by not attaching USB drives and other external media, the reality is that software upgrades to the offline system (i.e. Armory's signer) do need to happen to ensure compatibility from time to time. Excluding that, there is still the need to get transactions on and off the offline system, which provides the opportunity for an attacker if the online system is compromised.
For the RPi: this thread by TierNolan seems to offer an alternative to using USB devices for data transfer in order to help keep the offline system clean/secure. I'm unsure whether the GPIO being in use would mitigate outgoing transmissions by malware, but inclined to assume not.

I'm not an expert, but it certainly unnerves me to see a layer of the security model eroded like this - the suggestion of needing some sort of Faraday cage doesn't seem as excessively cautious as it used to be. Certainly a win for dedicated hardware wallets that only have the required components included

A little scripting goes a long way, then.