new macbook doesn't receive ALL of my text messages that appear on my phone

If you can’t send or receive messages on your Mac - Apple Support

Hope it helps.

Same issue on my existing Mac 12" after upgrading to Big Sur. One of my contacts I can no longer send messages to. They are on an Android and I get the message send failure now even though before Big Sur I had no issues sending or receiving messages with them on my Mac and my iPhone. Now I cannot send messages to them on my Mac, and only parts of the conversation I am having with them on my iPhone, will show up on my Mac. Then for another contact that's using an iPhone, I only received one of two messages they sent, but I was able to reply to them and they received my reply. If this can't be fixed, I would recommend back dating to Catalina.