Why can't the phone find service?

Hello,

I recently replaced the micro usb charging port and battery in my Amazon Fire Phone. My phone can no longer find service, even though I know that there is service at my home. The wifi connection is also much weaker than it used to be, even when the phone is right next to the router/modem. I doubled checked all the connections, and everything is in the correct place (at least it looks like it is from all the guides I've used). I've tried a hard reset and I've also taken the sim out and put it back in. The phone knows when there is no sim in and when I put it back in all it says is "searching" and "no service". Wondering what could cause this and if anyone could maybe give me some tips of stuff to try. I don't want to have to buy a new phone because I just put some money into replacing a couple parts.

Thanks a lot!