This cross has a reputation for not blooming. I personally think it has to do with the parents but I am by far an expert on Paphs.

Something I tried on my Roth crosses

If you are sure the light and warm temps with a drop in temp in the winter are being achieved then try fertilizing with a Calcium Magnesium fertilizer. There are many brands out there. I know DynaGrow has a Cal-Mag and many hydroponic stores carry brands.

Or with your normal fertilizer, start watering with 2 tsp Epsom salts to a gal of water.

This worked for me but not on that particular cross.