The server returned an error when broadcasting the transaction.
Consider trying to connect to a different server, or updating Electrum.
mempool min fee not met
It might be a "local transaction" with low fee rate which was probably rejected by the current server you're connected to;
check if the logo (on the left of the txn) looks like a 'blue computer' instead of 'green check' or 'gears'.
It looks like this:
The one in the image is a "local transaction" which can be deleted using right-click menu, "Remove".
After being removed, you can spend the coins it's trying to spend (read 'till the end before deciding to remove it if yours is a local txn).
The risk here is your transaction could proceed even though it was previously dropped by most mempools, because if mempools' size suddenly became lower, they may re-acquire it from the nodes that kept your txn.
To counter that, you must use at least one input of that specific transaction to ensure that it wont proceed.
To check the transaction's input, double-click the local transaction in the history tab, take note of the input's details (screenshot or copy), then proceed to remove the local transaction,
Now open "Coins" tab (View->Show Coins), and "Right-click->Spend" to the coins that has the same detail as your removed local transaction (CTRL+left click to multi-select before using right-click),
then proceed to the send tab and create a new transaction. Send it to yourself (same as cancel transaction) or to a new payment.
What you want to achieve is to invalidate the previous unconfirmed transaction for the canceled CoinPayments transaction invoice.