Something's not right, my Mint 18.1 VM works great with no issues retaining the license status. Is there any type of hardware change going on? Changing the hostname? Network interface change of some sort? Proper read/write permissions? Have you made any modifications to Mint?
You're not using something like an encrypted home partition are you? I've never actually tested this one to see if it works without permission issues.
It *should* work, especially if you're registering from the Terminal. If I had to make a guess, it could be read/write permission issue or corrupted MC settings file. If all else fails and as a last resort, make a library backup and remove the entire .jriver directory - this will reset everything and you'll have to redo everything. Just use this command in a Terminal for the last resort;
sudo rm -rf '~/.jriver'
P.S. Don't worry about using restores, they can (and have) been reset.
Just use the Terminal to restore the license file (the .mjr file) so you don't use up all your restores.