Ok well I'm not sure about the digging or mating because of the lack of info, but polys can go a long time not eating. Especially larger ones. You should probably switch to feeding 3-4 times a week so everyone you feed he will eat
If they are both around 8" then they could just be in breeding prep like was said earlier. You said they've tried breeding before but were unsuccessful. Did this behavior occur those times? Give it more time and just monitor them. Also what are the water parameters and temperature? If there's been a change in either of those, than it could be the reason it's not eating.
thanks all u people guys I cant add comas because im on youtube at the same time and everutime I type my computer lags so it would take me 30 minutes to make a full grammers sentence sorry guys