To confirm your original question - yes (for-sure) a Fish Tales DMD will work in a WCS. There were different manufacturers of DMDs for the BW games (Cherry, Vishary etc) but they all should interchange from the earliest Gilligans to the newest Cactus Canyon.
If something is not working, it is not because they are incompatible.
Therefore, if a DMD works in FT, you will need to find out why it does not work in WCS. Once you've done that, then definitely do as Coz suggested and get a Color DMD.