Mail app does not sync

I began using this computer around Thanksgiving, so just recently.  I operate on Windows 8.1.  When I began using my Mail app, all was well and it was a very useful tool.  A few weeks ago I noticed that I had not received mail.  This has continued and now my mail app is empty upon opening.  The only error message I have gotten is "*** Email address is removed for privacy *** could not sync" in the top right hand corner of the screen.  How can I fix this?  Also, my Store app is also not connecting.