That's the error I get when I try to send.
Deleted mempool.dat
restarted everything (armory, bitcoind, OS ubuntu 18.10)
rebuild and rescan db

and still get that error


it appeared after I sent transaction while having network problems, it stayed at 0 confirmations in armory for a while, when checked block explorer, it didn't exist, so I did "clear unconfirmed" that worked and cleared it but since then when i try to send that particular UTXO I get the error above.