I just waited out the 20 days while staking my 50,000 mint on a running wallet (I know it doesn't need to stay running but it was mostly up the whole time).
Then I saw two rewards come into the wallet that were "Generated but not accepted" (148 then 149 mint).
Finally I got a successful minting reward of 153 mint confirmed.
And now I'm no longer minting... "Not minting because you don't have mature coins"...
Umm, what? This doesn't make any sense at all. 20 days to wait AGAIN, in between every staking reward?
If this is how it works then it's a total waste of my time. This must be a bug in the wallet?
It's not a bug, it's a feature!
This is how all old PoS coins work; all coins inside the wallet have to mature before they can mint new coins.
MINT has a mature period of 20 days, it's no secret. Maybe you should've studied the coin's tech specs a bit more carefully....
It is a good system, only surpassed by the PoS 3 with masternodes.
Maybe MINT's devs are planning to shift, but for now this is the way it is supposed to work. And it works!