My Hotmail Account No Longer Syncs Up to My HTC One Phone (on Sprint)

For the last several days, my Hotmail account no longer syncs up with my new HTC One phone.  When I try to sync up, I get an Error message that says "Authentication failed.  Please check your address and password and try again."  When I go into the Settings menu and the Accounts and Sync option for MS Hotmail, I see a message that says "Sync is currently experiencing problems.  It will be back shortly."  Any ideas what's the problem?  Thanks for your help.