We have an Excel spreadsheet that connects to a SQL SSAS server through a data connection file and Excel Services. It has worked for months without a problem. Recently, we upgraded the SQL Analysis Services server that it connects to though, renamed the new server the same as the old one and verified we can connect to it by opening the Excel file in Excel. No problems there.
If I open the file in the web app though, it loads the initial screen and if I try to filter the data in any way, it throws an error:
An error occurred during an attempt to establish a connection to the external data source. The following connections failed to refresh: [data connection name from the excel file]
ULS logs show the data refresh request start and complete successfully though. I was also getting a warning that the data connection file was in an untrusted location but i added that to the Excel services options and that seems to be resolved.
Again, NONE of this was happening until we replaced the SSAS server. So how can there be problems in Excel Services or SharePoint??