Thanks.
eager to see what the problem is. You dont seem to be the only one.
I think they somehow reverted to an older database of the secret keys. Old keys 'start' to work but fail API verification (which is to be expected) but no newer secret keys pass Leonardo's start, so it's on LEO's end I think as it does not even try to connect to Poloniex..
If you didn't change your executable, your keys will always stay valid for leonArdo.
The "valid" keys (actually the first half) are built-in the executable itself. That is why Jonathan needs to re-build a version for every new purchase. So it doesn't depend on an external server or database to check on that.
And think about it: If it would depend on an external server to check the validity of keys, then all copies of leonArdo would stop working iof their server would be down, or if the company would cease its operations. Not a good model.
So, logically:
If you changed your executable, then I'd suggest you to revert back to the one you were using successfully before.
If you are using the same executable as before, then my guess is that Poloniex (if that's the one you are using - which one is it?) has banned your IP, for a reason or another. It does happen sometimes - too often, actually.
Try connecting from another IP. (And make sure there is no IP whitelist in place for your keys - I don't know if Poloniex has that feature.)
Or try deleting leonArdo's setting folder (or rename it to make a copy beforehand), in case some file was corrupted and leonArdo was somehow sending a corrupt key. That way, you'll be forced to re-enter your keys when starting leonArdo again, and you'll be sure that you'll be using the correct keys.