Subfolders are empty on iPhone 15 Pro Mail app after iOS 18.3.2 update

I recently upgraded to an 15 Pro and now all of my mail sub folder are empty on the phone (wasn't a problem before I upgraded)

The sub folders all appear as per my outlook/web email account and even new folders I create appear but are still empty. I created a new folder yesterday and transferred 3 emails into it, I can see the folder on my phone but it is empty

I am using Sky email in the UK which is run on the Yahoo platform. I can send and receive emails into the inbox no problem, so the setting for Sky/Yahoo must be correct. Its just the subfolders I cant see

Help please as I am having to manually move emails out of a subfolder and into the inbox (via web app or outlook) if I need to use them from my phone

[Re-Titled by Moderator]