Connecting to a different server or updating your wallet won't help here. Your transaction is invalid and any server will reject it.
As explained by o_e_l_e_o, your transaction is being rejected because it's trying to spend utxo(s) that has been already spent (double spending) or doesn't exist in first place.
What you have to do is to open the history tab and remove all transactions labeled as local, restart Electrum, recreate the transaction, sing then broadcast it. This should be enough to solve your problem.
This worked! Thank you so much. I'll say more later, but for now----THANKS!