@Rass
Hi, thank you for the feedback.
Please help to confirm the following information to locate the issue:
1. Who is the SIM card carrier? and is the carrier the same as that of your phone SIM card?
2. What is the hardware and firmware version of your MR600? please make sure the two external LTE antennas are installed properly.
3. Please show us a screenshot of Advanced->Status page and Advanced->Network->Internet page, you could also try to move the location such as near a window to see if it will receive any 3G/4G signal
4. If possible, you could also try a different SIM card especially from different carriers to see if it works fine on MR600.