Messages not syncing between MacBook and iPhone

So, I just picked up my new M3 Max MacBook Pro running Sonoma 14.3 (never owned or signed into another Mac product previously) and cannot get my messages to sync with my iPhone 14 Pro Max running iOS 17.3. It seems to display random messages dated a month ago on my MacBook other than what I have got since getting the MacBook, but those dates aren't even right, the messages are much older. Some of these conversations are regular texts while some are iMessage with iPhone users. My phone shows all messages. In the iCloud settings on my phone, it shows the last sync being September of last year, and hitting "Sync Now" makes it load for a second and then show the same, old date again. Using the message settings on the MacBook to force a sync provides the same result: loads for a while and then updates nothing. Am I missing something here or has anyone else encountered this and come up with a solution?