Blank screen?

Hello,

So I've been using two different accounts. One my personal I have already on app on iPad which stays logged in (*******).When I do reviews I have a separate account(*******) which I log into from Google/search bar. Now when signing onto the 2nd one it will log in the home page will show but when I click on mail icon it acts like it's going but it doesn't. More like a blank white screen. Am I doing something wrong? I've tried last night and see happening today.