Some messages cannot be sent/received on new Mac Book Pro.

Just purchased a new MacBook Pro running on Monterey 12.1. I can send and receive all iMessages on my old MacBook Pro (mid 2015) running on Big Sur 11.6.1. Selected cell numbers will not send or receive on the new Mac. Yes, all messages are enabled in the cloud. And I have selected SYNCH. Problem still not resolved. Help! Frustrating running back and forth between two computers. (All text messages can be sent and received from my iPhone.) Thanks.