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Could you try the procedure described in this page: https://wiki.teltonika-networks.com/view/RUTXxx_Firmware_via_The_Bootloader_Menu.
If that does not help, return the device or ask for replacement.
Regarding the issue, you are having kindly try recovering the device via bootloader menu firmware upgrade. You can do this by following the steps mentioned in this link: RUTXxx Firmware via The Bootloader Menu - Teltonika Networks Wiki (teltonika-networks.com)
Kindly use the RUTX12 firmware 2.06.1: RUTX_R_00.02.06.1_WEBUI.bin
After the device is fully recovered upgrade it to: RUTX_R_00.07.01.2_WEBUI.bin without keeping the settings.
Let me know the results