The hackintosh community has been troubleshooting iMessage activation issues for a decade. Activation is tied to the Mac's serial number, so you either need to

The hackintosh community has been troubleshooting iMessage activation issues for a decade. Activation is tied to the Mac's serial number, so you either need to work with Apple Support to get your Mac's serial number off the blocklist, or you need to change your Mac's serial number to a unique and valid one that isn't blocked. https://www.tonymacx86.com/threads/an-idiots-guide-to-imessage.196827/ https://www.tonymacx86.com/threads/an-idiots-guide-to-imessa...