As a dwarf breeder, I can tell you, we try to stay away from breeding false dwarf BUCKS to true dwarf DOES. I would suggest getting a bigger female for your false dwarf (unless you know he has the dwarf gene) just so she doesn’t have problems.
As for her not breeding, one of my females did the same thing, but I put her back with the buck that night and they bred. Check for a swelling vent next time you put her in (usually if you put them together and they don’t breed but you check later on the doe she is swelling and ready to be bred). I hope this all makes sense!