Nighthawk M6 invalid SIm

Hi,

I got a Netgear Nighthawk M6 from Optus and I changed the wifi offloading setting then I changed back to the original setting. I also enabled the Ethernet port as well.

Problem is now it comes up with an invalid SIM error.

How should I fix it? Is a factory reset safe?

Plus why would making some settings changes like this invalidate the sim?

Thanks

Ward