Help please

I can’t get my sim to work. It will work in my old Apple XR but not in my 16+. Any ideas before I ditch it.

What happens when you try.
Is your phone sim locked or restricted

Not restricted. It was bought sim free. It won’t connect to the network.
I had an ID mobile sim and wanted to change to Lebara. The first sim didn’t work so they sent me another. That didn’t work in my 16+ but did work in my old XR. When I put the ID sim back in it worked. I tried to change it again and this time not only did the Lebara not work but the ID also doesn’t work now! I’ve booked a visit to Apple for tomorrow but if you have any idea what is going on????

Sounds like phone is not reading the sim card possible phone issue.