Quote from: hashtag on Today at 03:54:05 AM

-zapwallettxes fixed it

just to clarify that deleting mempool.dat was the first thing I tried but it didn't help

Probably worked together with 'deleting the mempool.dat file' since it also contains that transaction.

I know this is late but if it's just an issue with a single unconfirmed transaction,
a simpler solution is to create a signed transaction that can be broadcast outside of Armory.

After using "Clear Unconfirmed", create the same txn using the cold-storage method but instead of using Armory to broadcast, just copy the the "RAW TX (HEX)"
and broadcast it using an online service like: https://live.blockcypher.com/btc/pushtx/ or https://blockstream.info/tx/push

If you don't know how to get the Signed Raw Tx, follow this:

Click "Send", fill up the transaction info: fee, recipient, amount, etc.
On the same window, check "Create Unsigned", then click "Continue"
On the next window, click "Copy to Clipboard", then "Continue"
Next, paste the copied text, click "Sign", "Continue" then type your password
Click "Copy Raw Tx (Hex)".
Lastly, go to an online push service and paste and send that signed RAW tx.

After getting one confirmation, the conflicting transaction in your mempool or Bitcoin core's wallet.dat will be dropped.