Sim not supported

If your iPhone is factory-unlocked meaning it can work with any carrier SIM, then maybe the SIM you are using is "broken" and needs replacement OR the SIM needs to be activated from the carrier first before you can use it.

In either case, you want to speak to your carrier company!

Sounds like your iPhone is locked to a cellular service provider that is different to the one the Sim card is for.

Where did you buy this iPhone? Were you told it would work with your specific cellular service provider?

Is it a used iPhone?

Your friend would need to remember where he bought it to figure out what network it is locked to.

You can also call Apple Support directly and they should be able to tell you: https://getsupport.apple.com/

or: Contact Apple for support and service - Apple Support