Hello,
It is recommended to use both the mobile antennas .
Further could you check in the storage if the storage memory or sim memory is not full.
Also have you tried inserting the sim card in the mobile or other device ? Just to check if sim card is working fine in sending and receiving the sms.
Mobile information meaning Status>Network>Mobile .
After trying all above please try to re-flash firmware in boot loader mode .
Steps for updating firmware in bootloader menu could be seen here:
https://wiki.teltonika-networks.com/view/RUT9xx_Firmware_via_The_Bootloader_Menu
I hope it helps
If you need more help please feel free to contact back.
Thanks .
Have a nice day.