Hello NnamO,
Running an older version of the GPS firmware could prevent the on-board GPS receiver from working properly. It should not prevent individual SMs from registering. Having said that, it is recommended to upgrade to the latest GPS chip firmware at your convenience, as documented in this KB article.
Be adviced that GPS fw upgrade could take a long time (8-12min in some instances). Do not reboot or power down the unit until the GUI shows the reboot button highlighted in yellow and shows a notification in the Notification area of the GUI, that a reboot is required. Not doing so will disrupt the firmware update and will require the GPS chip to be recovered (can only be performed by Cambium Support).
Regards