i have total 300 sim 800l module, last week we had applied on the field now they are not able to connect to the network.
even i had checked all things but it seems perfect (voltage, current, antenna and etc). even module are original but all module are not working after 6 days one by one goes down and gives AT+ CREG (0,3) output. even not able to latch on a network.
we had also tested with/without antenna but same problem was there.