Office Online Server "An item with the same key has already been added" No FileSourceId found for servername.
I was experiencing errors rendering Office Apps from my SharePoint farm after attaching a new Office Online Server to he farm. I saw the following error in the browser: Microsoft Word Web App Sorry, there was a problem and we can't open this document. After some troubleshooting, I found this error in the ULS logs of the Office Online Server (Office Web Apps): No FileSourceId found for servername. (servername was the name of my SharePoint URL) I solved that by running the PowerShell cmdlet: New-OfficeWebAppsHost -Domain servername This should have solved my problem but I accidentally entered my domain twice (corp.domain.local) I now received this error in my event log on the Office Online Server ID 1309 Process information: Process ID: 9999 Process name: w3wp.exe Account name: NT AUTHORITY\NETWORK SERVICE Exception information: Exception type: ArgumentException Exception message: An item with the same key has already been added....