New iphone

What happens when you try? on what iPhone model? with what iOS version?

Have you followed these instructions:--> Set up your iPhone or iPad - Apple Support ?

and/or these:--> If you can't activate your iPhone or iPad (Wi-Fi + Cellular) - Apple Support

Regards

Giulio

See this support article about that:--> If you see 'invalid SIM' or 'no SIM' on your iPhone or iPad.

If the issue persists, contact Apple Support directly, using this link:--> Apple Support

Regards

Giulio