iOS 8.4 mail problem on iPad

A firend has updated their iPad to 8.4 and since then their email has stopped working. You get a menu at the top of the screen with Flag, Folder, Bin, Forward and Create icons but the rest of the screen is blank. Have tried rebooting but stll the mail client fails to work. Everything in settings is okay and problem has only occurred since the upgrade to 8.4 - it was working fine before.