First, please check if GPS monitoring is enabled for your device on the RMS.
To check monitoring options for your device go to the RMS web page, Left sidebar panel (Management → Devices), and click on Devices submenu. Select your device and move your mouse pointer to the top on the Monitoring menu and select Set update period (Monitoring → Set update period).
More information about monitoring menu you can find here: https://wiki.teltonika-networks.com/view/RMS_-_Monitoring_menu#Set_update_period
If GPS monitoring is enabled, but you still do not see any GPS related information on the RMS, then please send me your router serial number via private message.