Social Media Notifications not working - iOS 14.3 and 14.4 beta

I have a bit of an odd one here. On both iOS 14.3 and the 14.4 beta, all is well when in a factory reset mode (as in, factory reset, start the phone, install a couple of apps and that's it). When I restore a backup, apps such as Instagram and Twitter do not give me notifications or badges. Given that this only happens when I restore my backup, I'm struggling to figure this one out.

All settings in both the above mentioned apps and the Settings page match. I checked them before restoring the backup and after. They're identical. The only difference I can conceivably think of is that, after the backup, my Apple Watch is paired. However, I also don't get the notifications there either so that could just be a red herring.

I've restored the phone a couple of times. I've done it via Recovery Mode and yet, as soon as my backup is restored, the notifications break again.

Truly at a loss as to what else I can check given the notification settings within the apps and with the Settings page are like-for-like.

Any help would be greatly appreciated.