I had to resuurect my nexus 5 (820) after my other phone's battery is dead and you need to take the screen out to do it and i couldn't be bothered.
Fast forward, I replaced the battery for the N% and put my sim in. I thought it was fine as 4g was working. Getting SMS etc. Then when i went to call someone a day or so later it didnt work.
I changed the preferred type to 3g to test and it just comes up with no signal. From there i changed the ROM to a new android 9 rom. Still no difference. I tried apn settings etc etc nothing.
I have a feeling the bands are not supported with the simcard i have.
But is there anything else i can test before giving up on it?