You need to be more specific. If you mean the emoluments clause, I think it's more accurate to say that it's hard to verify whether he meets "the requirements set forth in the Constitution." If you know of an instance of his business accepting a gift from a "king, prince or foreign state" since he's assumed office, then he's actually in violation.
> He isn't being impeached because his party controls both houses.
There is also that. Although I think a not insignificant fraction of that party would much prefer Pence, and if they were going to oust him doing it as far from the next election as possible would seem preferable.