Mail not showing up on my iPad?

I am setting my old iPad up for my mother. I added her two email accounts with accurate id's and passwords. But when I go to the mail icon, no mail shows up in her mailboxes. I checked from my desktop and there is mail in her inbox. I went to through the Website on the iPad and put in the id/password and it shows that she has mail, but it still doesn't show up by going through the mail icon/function on the iPad. What am I missing?