Yahoo Mail not downloading

Since reinstalling Yahoo on my husband’s replacement iphone11, he has had endless issues with his mail either now downloading, partially downloading or showing ‘This message has no content’. I have followed all the guidance online to rectify this and his mail is now, at long last, downloading his emails but some still show this message but when clicking on them, the content is downloaded. During this ‘frustrating’ time, I had to remove our VPN because one of the Apple experts said it may be interfering with the email’s software, but I will now reinstall it again for the obvious protection it gives. However, have our problems been as a result of one or more of the Apple updates - a glitch possibly? - as I can see others have encountered the same issues?