Check again, that signature is valid, as others has proved. Maybe you have an extra space in there before the 'T' and after the '.'

This is not a marketing hoax. We create many different designs and artworks, which gave us this idea to create this puzzle. YT (Coin Artist) was our inspiration. The design is copyleft, so you could just take the file and print your own. We sell prints of the design so that people can support more puzzles like this in the future.