For an unexplained reason the e-mail app on my iPad 6 gen will not load.

Double tap your home button to bring up the app switcher. Slide the mail up to force close it (along with other apps you don't need immediate access to), then tap your home button once to return to your home screen. See if the mail app opens normally.

After you slide the apps up with your finger (especially the mail app, which is the one you need to force close), tap your home button once. That will take you back to your home page.

I'm glad.