While on vacation recently, I had great difficulty with MS Outlook on my iPad and iPhone. I have a Microsoft 365 subscription, which includes the mobile apps. Outlook stopped working and kept asking me to enter my credentials. I would enter what I knew to be the correct password, but it still kept asking me to enter my credentials. Eventually I solved by by deleting my account, uninstalling Outlook, reinstalling Outlook and re-adding my account. (I didn't lose anything because both devices are set up using IMAP.)

How, however, I am faced with having to put up with ads appearing in my inbox on both devices. When I ask why am I seeing these ads, it says it's because I have the "free" version of Outlook. Try as I might, I can't figure out how to install the paid version of Outlook (which I had before). Will someone please explain to me how I do this? Thanks very much for any help.

I have an iPhone 14 and and iPad Pro.