My girl struggled with the TOTW Pacific stream as well. She was (is) an incredibly picky eater.
Try mixing in raw mince meat or a few broken up sardines into their kibble. Put a tablespoon or two of hot water in and mix everything around as well. That seems to make it a bit more palatable.
This usually works for me if I'm having difficulty getting my girl to eat.
Failing that, have you tried the other TOTW flavours?