I found the problem. Our ISP has changed something. The displayed GSM network name changed to another. I don't know what was the previous APN but i created another APN with the server name of the old...

Hi, I have 2 modem-router 4G, TPLINK M7350 and MR600 with 4G SIM (French ISP). Since 1 week, my 2 router stopped to find 4G signal, on the same time. SIM work well on smartphone. I tried with a 3rd...