Hello tower,
I agree with casxyz, If they have already lived together before, then maybe he is just taking longer to settle. and he is probably out more than you realise, coming out when nobody is around. How are things with him now? Mine live out side so they do there own thing all day and sleep quite early at the mo, Not sure if this is the same with indoor chips. But animals as well as humans can all take to change differently.
I hope that all is well and you let us all know how things develop, lots of new chip owners on here will have the same questions and worries, so your not alone.
Sarah.