iMessages not syncing automatically between Mac

My MAC is 15.6.1 (24G90). My IPhone Pro Max 16 is 18.6.2.

My IMessages between the two devices are NOT automatically synching. I have to manually synch on each device.

I Cloud and Apple are signed into the same PW. I have tried restarting each device, but have had no luck.

Is this an Apple programming glitch or is there anything else I can try.