It is showing as confirmed in blockchain.info
Hmm, then I don't know what can be wrong.
Might be issue with private key format (unsupported format) ... but in this case I would expect some warning message from electrum.
Do you know in which format your prv. key is? (BIP38, WIF, mini)?
Mabe you can try it using other clients like coinomi, mycelium ... no need to perform the sweep (just to chek if prv. key shows you the relevant address and amount ).
Sorry, I'm just shooting ideas. My sweeps always went smooth, never experienced such issue.