I have configured Messages app on my Mac. Any SMS that I receive on iPhone is synced on my Mac. If read the SMS from iPhone it is marked as read on Mac and vice-versa.
But if I delete any SMS from iPhone, it does not get deleted from Messages app on Mac. The same issue is other way round.
What is the issue here and how can I resolve it?
Update 1:
This is how my preferences are set.

Best Answer
I ran into the same issue with macOS 11.0 and I am not sure if it happened because of Big Sur using the new Messages app. What resolved this was to go to my Preferences > iMessage tab and select the Enable Messages in iCloud option by checking the checkbox. Then, click the button that says sync now and they will sync.
Hope this helps!