iPhone 7 Plus SIM card not supported after reset

Where did you purchase an iPhone 7 Plus for $2,000? The iPhone 7 Plus was released in 2016, and discontinued in 2019. It is now considered a vintage device by Apple. A not supported SIM sounds like the phone is locked to another carrier than the SIM you are trying to insert. Only the carrier that locked the phone can unlock it.

Sounds like the phone was hacked to illegally remove the carrier lock.

That phone is long obsolete, by the way.

It was discontinued in 2019 and can no longer run a supported version of iOS.