Lumia 635 error message "SIM card is missing or invalid"

Does anyone at all have the answer to this problem of the Lumia Nokia 635 Sim card message 'Missing or Invalid SIM card'? I have recently switched supplier (but not network) and find that the first and second new SIMs haven't cleared this error. I'm being sent a third SIM to try but I'm not confident that'll solve things. The phone is not locked. The Sim is inserted correctly. The supplier systems test showed no problems. Microsoft is no longer supporting microsoft phones it seems in the UK!!

Is this a known problem with Lumia 635's, does anyone know?

I'm having a similar problem, as well:

Lumia 635, locked to Vodafone UK, no SIM works. Got a SIM from Vodafone UK, Lumia 635 STILL doesn't work, but the Vodafone UK SIM turns on anything it's put into.

Now Vodafone are proposing some really ridiculous solutions, like taking the phone across the Northern Irish border, where it's meant to turn itself on and work properly. I'm no telephone repairman, but I just don't think this is going to work.

I'm reluctant to take the phone in for repair because it's no longer in warranty and a quick scan on eBay tells me it's just not worth as much as the shop is likely to charge to try to fix it.

Is there any chance this is a firmware issue? The phone is running Windows 8.1 and apparently not eligible for the automatic upgrade.

Please try to contact our United Kingdom support at: (0)344 800 2400.

Chat support is also available at our Answer Desk page. Click on the Contact Answer Desk button.

Lumia Care Point appears to be a 'USA Only' facility and I am in NW England (UK), so unable to access this service.

Thanks for trying, Joe.

Hello, Ross.

Thank you for posting your query to Microsoft Community. I understand that you're having issues with your SIM not detected by your Lumia 635.

I recommend that you take your phone to a Lumia Care Point facility. Please use the form found at the Lumia Care Point Locations website, to search for a facility near you.