I have the same issue than yesterday :
The first time I try to send bitcoin to a valid recipient address I have the error message : The transaction that you just attempted to broadcast has failed with the following error : Missing inputs
This means you are trying to spend outputs that just do not exists. Something is off with your blockchain data/Armory DB state
For the second try, I have the "Coin selection failure" with the message "Coin selection failed with error : Invalid spend value"
Could you please help, knowing that I've done all that was suggested above (including 60sat/byte for the transaction) ?
This means you are trying to spend more than your balance allows for. Reduce the spend value, use the MAX check box or lower the fee to hit something usable.