Old iMessages not syncing on new M1 MacBook Air

Hi,

I am unable to get old iMessages to sync across between my iPhone and my new Mac. New iMessages appear to come through.

I have tried:

1. Signing in and out of iCloud on iMessages on my Mac
2. Adding 1 phone number and 1 email in the Contactable on section on both Mac and iPhone (they are the same)
3. Adding 1 phone number only in the Contactable section on both Mac and iPhone
4. Attempted to follow a range of possibly out to date advice articles from apple and external websites - none yielded success.

Equally I am unable to turn on/off iMessage in the iCloud settings on my Mac.

Any thoughts?