iPhone 6 no service/searching

Hello all,

I have a iphone 6. The problem started when the phone started searching/ had no signal. So i replaced the lightning dock, with the antenna. After this i had service again. After laying it down for a while, i turned it on again today, and now i wont get service on it again. Everything else works on the phone. Things i have tried:

-Hard reset

-Reset all network settings

-Restore

-Check if the antenna cable is tight

The strange thing is, that it worked after i replaced the lightning cable, but not now. Any suggestions? Thank you!