My text messages are not synching on my iPhone 13 and my MacBook. Help!!

Hi, and welcome to the Apple Community :-)

See if these Apple support articles will help.

How to forward SMS/MMS text messages from your iPhone to your iPad, iPod touch or Mac

https://support.apple.com/en-us/HT208386

OR

View this discussion answer about using iCloud to sync messages

https://discussions.apple.com/thread/253410116

Hope this works for you :-)