I have seen this error with altcoins before or trying to send to a NON Bitcoin address.

Double check the address your sending to is also valid Bitcoin address.

Some steps you should take if the above is not correct.

1. Backup your wallet file make a copy of it and put it somewhere safe.
2. Open your wallet file > new/restore and and recover from seed and try again.

Please report back once you have checked the above.


The keys are Pay To PubKey Hash (P2PKH}

Also make sure you only download Electrum from the OFFICIAL source

https://electrum.org/