We have the same situation since monday the 6th of June. Have been in contact with MS support beeing sent from SP team to PBI team to Office team with no success.
Online refresh using datagateway kind of corrupt the file for Ecel applciation. It's working fine with online version.
Typical Event viewer message seems to indicate that excel can't get the datmodel:
The description for Event ID 25 from source MSOLAP$LocalCube cannot be found. Either the component that raises this event is not installed on your local computer or the installation is corrupted. You can install or repair the component on the local computer.
If the event originated on another computer, the display information had to be saved with the event.
The following information was included with the event:
msmdsrvi_xl.rll
1036
The message resource is present but the message was not found in the message table
or
The description for Event ID 19 from source MSOLAP$LocalCube cannot be found. Either the component that raises this event is not installed on your local computer or the installation is corrupted. You can install or repair the component on the local computer.
If the event originated on another computer, the display information had to be saved with the event.
The following information was included with the event:
An error occurred when loading the 'Microsoft_SQLServer_AnalysisServices', from the file, '\\?\C:\Users\xxxxxx.xxxx\AppData\Local\Temp\{38A7CB23-B6E3-47B2-AB59-DE7D9B5C53EA}\VertiPaq_E61D01719804DCA87E8\A5407185E29D4BBFBE17.7.db.xml'.
The message resource is present but the message was not found in the message table
Also I have information at file opening sying:Offline downlevel migration succeeded.