LTE is not working after battery replacement

I recently replaced the battery on my dad's iPhone 5s. Everything went well, hard reset after replacement and no other issues except LTE signal is not working now. I can reliably get a 4G signal and connect to wifi though. Also can no longer use the phone as a hotspot (I assume you need an LTE signal to run as a hotspot) for his iPad.

I've tried several things, including multiple hard resets, toggling Enable LTE in settings, resetting network settings, even restoring the phone as new. My SIM card connects to LTE on my 6s so I tried swapping them out and it won't connect to LTE with my SIM card either, still only 4G, so it makes me think there is some kind of hardware issue going on. Is there something I could have damaged or unplugged during the repair that would prevent an LTE signal but still allow 4G and cellular services to connect?