MR5200 - Mobile Broadband Disconnected (EE)

Hi, I realise that this has been discussed many times before, but I can’t seem to find an actual answer that solves the issue.

I am trying to use an EE (UK) 5G enabled data SIM in my MR5200, but I am not able to make a connection. I keep seeing the message Mobile Broadband Disconnected. I have checked the APN settings for the SIM and I am certain that they are correct. I have tested the SIM in an M1 router and it works without any issue.

The firmware is NTGX55_12.04.17.00 and the SKU is MR5200-100EUS, hardware version is 1.2

Any help would be greatly appreciated