Lost iMessages and iCloud sync issues after iPhone upgrade

HI.

I recently upgraded from an Iphone 14 pro to an Iphone 17 pro max. Shortly before upgrading (maybe 2 months ago) i noticed that i lost about two years of messages. Importantly, with a very special person. I did not delete them. My imessage settings have always been on "never delete/always keep".

I have tried updating my phone, turning icloud imessages off and on, turning imessage off and on with no luck. I have about 320,000 imessages in the cloud, but when i hit "sync now", they either don't sync, they sync maybe 200 or sometimes 5 at a time. I have increased my icloud storage to 2TB, and im using about 320 GB total.

Please help. I am desperate to get these messages back.