No Options for Apple Intelligence after reinstall

Hello,

After I accidentally installed the beta version of MacOS Sequoia 15.4 on my Mac (long story), I ended up downgrading the OS and restoring from a time machine backup. I am now back on Sequoia 15.3.1 (Build 24D70)

However now, my mac appears to be stuck without apple intelligence. I have attached a photo to show what I mean.

Failed attempts to fix:

• Re-installed MacOS Sequoia from recovery menu.
• Changed language, region, & siri to British English and restarted mac.
  • Doing this makes the UI to enable apple intelligence appear, but enabling it does nothing.
• Disabled Siri and restarted mac, then re-enabled.

Apple Intelligence is currently shown to have a size of 5.45 gb in the storage menu. Leaving the mac on overnight w/ wifi + power has not increased the file size.

Is it possible that files are corrupted? If so/if it's something else, any tips on how to fix the issue would be much appreciated.

Cheers.