Macs do not allow use of phone number for Messages

Just occurred the past few days - no clue why. A son just asked via Messages why my messages were coming from an email address rather than the phone number I've always used. I text from my iPhone, iMac and MBPro. After checking, the two computers are using the email adds, while the iPhone is using the phone number. Depending on which I text from, I have two separate text threads now going to some people. The computers do not receive the messages generated from or sent to the iPhone and vice versa.

Opening iMessage Prefs on the Mac - settings pane, neither the "You can be reached for messages at," or "Start new conversations from" fields list my phone number - only three email accounts. But the iPhone, in Settings-Messages, the "Send & Receive" is my phone number, which is what I'd like to - and had been for a long time - use on all devices.

Assuming I've just inadvertently messed something up, but the computers don't even list the phone number as a possibility.

Any ideas greatly appreciated!