You say the milk is homogenized, but you didn't say if it was pasteurized as well - I presume it is?
Also not clear whether the milk is gelling at all and simply not reaching a clean break, or if there is no gelling whatsoever.
Three possibilities come to mind:
1. Thermo culture is not very active (too old, not stored well, etc). You may not have noticed it when using raw milk, as the milk probably had some native starter cultures anyway. If the acidity is not dropping, coagulation will be much slower. But I'd expect some by a few hours time...
2. Rennet quality is low, or not enough used - you generally need more rennet with bought milk.
3. Milk was ultra-pasteurized. Denatures protein and does not coagulate well.