The dollar bill unit did originally come out of a game king from what I was told it definetly has not been updated in a very long time if ever
If it came from a Game King, it is likely programmed with ID024 (Netplex) protocol. It's not compatible with an IGT Player's Edge Plus machine which we're assuming your machine is, but you haven't posted any photos of your machine and you originally had this post in the IGT S+ (reel slot) section.
First, can we confirm that you have a Player's Edge Plus machine? If you're not sure, post a photo or two of it.
Second, if you do, you'll need to get the validator reprogrammed if it has a flash chip, which WBA 12s have, to ID022/ID023 for it to work on a PE+ machine, or get a different validator that is already programmed with that protocol.