Have you sent any transactions prior to that? Can you examine the transaction and see if you can see the unspent outputs in the address on a block explorer? It's best to not send transactions when the client is out of sync since the client can construct a transaction with spent outputs.
It's most likely an issue with the small fee. Run bitcoin core with -zapwallettxes and you can resend it.
I have sent many transactions before, last 2 months ago with similar amount and same fee.
I don't know how to examine a transaction as you said.
I'm now syncing the client. will report back when finished.
It's possible that your transaction is a double spend because you are not synced. This would make your transaction invalid and thus rejected.
You cannot cancel a transaction. Once it is broadcast, you cannot abort it.
However, you can remove the transaction from your wallet and resend it. First you need to sync your wallet. You can enable pruning to save space.
To enable pruning, add
To the bitcoin.conf file in your data directory.
Then follow the instructions at
http://www.achow101.com/2016/07/Bitcoin-Core-Troubleshooting#stuck-tx to fix your problem.
Ok didn't know pruning was a thing, now syncing everything up (the huge bump in space freed was weirdly satisfactory to watch, in case you were wondering), will report when finished (might take a while).
Even if the transaction was a double spent, shouldn't it show on blockchain anyway?
