You can double check your 12 word seed... create an "offline" copy of this website: https://iancoleman.github.io/bip39/

The instructions for creating the offline copy are at the bottom of the page. After you have done that, open the offline copy in your browser. Then do the following:

1. Put your 12 word seed in at the top as the "BIP39 Mnemonic"
2. Under "Derivation Path" click "BIP32"
3. Set the "Client" dropdown value to "blockchain.info"

You should be able to see the addresses for your account at the bottom. If these addresses do not match with the one that you deposited bitcoins to, chances are that you got the mnemonic wrong. How that happened if you took a screenshot is beyond me. I could only guess that there was a bug in blockchain.info and the mnemonic they displayed was not the one that got set up on your wallet ID.

If the address does match, at least you'll be able to use the matching private key to sweep or import that address to another wallet and recover your coins.

Wow! That is quite strange! Cause those two are exactly what you need to have access to your account most especially the 12 phrase in case you lose your password. First question I will ask is, did you by any mistake drop those details you wrote on paper carelessly? That is what I would think first anyway. If you did and your details are correct, then it may be a browser error, just try again later or on another browser. I have never heard of such issue before with blockchain.info anyway.

Also, no matter how desperate you are to get that wallet back, don't ever give those details to anyone.

Lastly, if you are able to resolve this, I will also advise you use a desktop wallet if you have a SECURED PC that helps you have access to your private key. As far as I know, they are more secured than Web wallet where there is a complete third party in charge of your coins. I will recommend Exodus wallet, though new but great and newbie friendly. Note that some details you need to always keep carefully to keep your assets safe in case you have them directly at your disposal are (Main password, recovery phrase and your private keys).