@maxv 

Please check if the APN is correct on the router settings page, if not, create a new profile to enter correct APN.

Besides, is the 4G signal strong and stable in your area? If so, you could also try to change the network mode to 4G only to see if it works better.

Hope it helps!

@Marcia.Zhang Yes, it was one of my first try. Any how, the MR600 has been removed and changed with another router (different brand) that worked perfectly with the same setting. I believe that the MR600 need servicing. Quite disapponted because it failed after just a month of work.

@maxv If you tried that and you can get IP address from the SIM card, but no internet, you can try manually set up DNS to 8.8.8.8 and 8.8.4.4 in the DHCP module( Advanced--Network--LAN settings--DHCP server), then test it.

If it still not working, please send us the router's hardware version, firmware version, system log and the APN settings page.

https://www.tp-link.com/en/support/contact-technical-support/#E-mail-Support