SMARTY SIM not working in Netgear Nighthawk M1 Router

I've been using my SMARTY Data SIM in a Huawei E5577 mobile router for a while without any problems at all.  I have purchased a Netgear Nighthawk M1 - MR1100 - 100 LTE router and the SIM isn't working in it.

After inserting the SIM and powering up the Nighthawk M1, it recognises there's a SMARTY SIM inserted.  However, I cannot get online as the router says 'Roaming Data Disabled' and 'Mobile Broadband Disconnected.'

I have tried a Tesco Mobile (O2) SIM in the Nighthawk and that works perfectly; it immediately recognises the SIM, automatically populates the APN and works straight away.

I replaced the SMARTY SIM back into the Huawei E5577 router and it worked immediately, recognising the 3 network at 4G.

Please let me know what I need to do to get my SMARTY SIM working in the Nighthawk M1.    I know the router works as it works with an O2 SIM.  I know my SMARTY SIM is fine as it works in a different router.

Or is it just that SMARTY (3 UK) isn't compatible with this device, in which case I will have no option but to close down my SMARTY account.

Please let me know what I need to do.

Thanks,

Paul