iPhone 7 invalid sim / SIM card failure

I have an issue on my iPhone 7. It has an error message in the service display which says invalid sim. I also get a pop up box in middle of the screen saying SIM card failure. I have changed SIM cards and also done all the steps on site still issue there.

I’ve also been to my local Apple store where they did a iTunes reset and the error message changed to locked sim. So I went back to my service provider for a new SIM card and when that was put in the issue came back.