iPad email problem

[#1]

Until a couple of days ago, I was receiving email on my iPad without any problems.  Now, when I open Mail, items 'arrive' in "All inboxes" and "Unread"(showing as a number against the folder name) but when I open those folders, it says "No Mail" or "No Unread Mail" and there is nothing there to see.  When I open mail on my iPod or on my laptop (in Outlook), the mail items are there to be seen.
Could the iPad problem be something to do with a recent software update to IOS 9.1 or is likely to be something else?
Any suggestions on how to fix would be appreciated.

[#2]

Have you rebooted your iPad?
Had a similar issue with one recently when deleting accounts.

[#3]

Thanks.  Rebooting didn't have any effect.  But I then tried holding the Home button down for 10 seconds and that seems to have cleared the problem.  I can see the items in my mailboxes again now.