Apple Watch S4 from Europe in USA

Hello,

I recently moved to the US from Switzerland. I had to get a new iPhone because mine from Europe wasn't compatible with Verizon. Now I have trouble pairing my old Apple Watch to that new phone. Whenever I try to connect it, it just stops and take me back to "Pair New Watch" and "Pair Existing Watch" again, I'm trying to connect it for days.. I think its GPS + Cellular.