iCloud subfolders gone missing in iPhone Mail!

Hi,

I have an issue with my iPhone 12 mail app.

I use my Apple iCloud account for email.

I am unable to see/access my subfolders, so cannot read the email that I have previously moved into there.

It only shows the emails that are in the parent folder, not the subfolders (or the contents of them).

However I can see it on my mac, and also online using the iCloud site.

I can move emails on my phone into these subfolders, but cannot access the email afterwards.

I've tried signing out and then back in again, with no luck.

I've tried reinstalling the mail app too

I updated to 16.0.3 yesterday to see if that would help, but it did not.

Bit stuck now...

Anyone else seen this issue?

Thanks

Jonathan