Working on a client who was the victim of their previous IT company over using Microsoft Office 2010 Pro Plus licenses on workstations. This caused them all to have licensing errors and required the client to switch to a Microsoft Open License agreement that they had previously for Office 2010 Standard. After uninstalling and re-installing the software, the Microsoft Outlook 2010 client repeatedly asked for credentials even though they were entered correctly. Stumbled across the Microsoft Support and Recovery Assistant for Office 365 in my Google search for the root cause, so I gave it a try. This tool was child's play to use and within minutes found that Microsoft Outlook 2010 needed Service Pack 2 installed in order to be compatible with Office 365. Installed this patch and the client immediately connected. Thanks for the new tool Office 365 Troubleshooting Tool Microsoft.