Symptom:

When trying to open a document in Office 2013 ProPlus from Office 365's SharePoint environment, you are periodically prompted for credentials to SharePoint Online, OneDrive, and Lync Onlinet (using your email address and password).  Additionally, the affected users are those that have been synchronized from an on-premise Active Directory environment via ADFS.

Side Note: Not sure if this is relevent or not, but we noticed this started to happen after upgrading our ADFS Proxy Servers to Server 2012 R2 (ADFS v3).

You are prompted with the following Sign In box:

Call us overprotective, but we need to verify your account again before opening this document.

Once you try signing in, you receive the following error:

We are unable to connect right now. Please check your network and try again later.

Inside of the Lync 2013 client, you might see the following dialog as well:

Credentials are required

Lync needs your user name and password to connect for retrieving calendar data from Outlook

Solution:

This error is caused by a variety of different issues.  Please try all of the following below.

If you have a single client having issues

• Clearing cache of Internet Explorer
• Running an online repair of Office 365 ProPlus
• Switching Accounts inside of Outlook (File->Office Account->Switch Account)
• Deactiving office from Office 365 settings and reactivating

If this is a widespread issue on multiple machines in your environment

• Verify all proxy servers are functioning
  • If you have multiple proxy servers, ensure your Network Load Balancer is functioning correctly
• You might be hitting a known bug with the Office 2013 Suite.  See the following KB article on how to try a workaround (this was the fix for an environment I worked on using ADFS and Server 2012): http://support.microsoft.com/kb/2913639