IPad kicked me out of my mail on the app, but on iCloud.com I can log in to it. I have no clue how to fix this!

I need my email available so I can see what my coach is telling me PLEASE HELP!

is there a way to fix my email through the app so it lets me log in? If so please respond at earliest convenience! I can log in online but I need the app as well. I paid a good amount of money for this device and saved up a whole year for this and I would expect everything to work.

If you do have the answer to this question please respond.

Thank You.