@Joseph-TP 1. i am sure the SIM card is inserted correctly and firmly in the SIM card slot ... it was working with the same card few days ago 2. i tried Restarting the Router with the SIM card still...

I have a 4G Router TP-Link MR6400 with firmware 1.6.0 0.9.1 v0001.0 Build 181022 Rel.40644n when I start the router I have the error No SIM Card Please insert your SIM card. ** it was working good...