Access is denied
Problem
When starting the modern Office addin, it immediately fails with error "Access is denied".
The issue is an corrupt IE localStorage that is necessary to run our addin. Should only happen on Outlook for Windows or Outlook for Web when using Internet Explorer.
For advanced users, a lot of background information to the issue can be found here: https://stackoverflow.com/questions/13102116/access-denied-for-localstorage-in-ie10
Solution
There might be different reasons for the issue, so please try the following steps one by one and check if it is working again
1 - Solution: Clear Registry Cache
Close Outlook
Open Windows registry with tool regedit (Help)
Open the following tree path:
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings\5.0\LowCache\Delete the whole key "Extensible Cache" including all subkeys
Open the Cache folder
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings\5.0\Cache\Delete the whole key "Extensible Cache" including all subkeys here too
Restart Outlook and check if it is working
2 - Solution: Set integrity level
Close Outlook
Open a command line - cmd (make sure to not run as administrator)
Run the following command to set the integrity level for the AppData/LocalLow correctly to "Low"
icacls %userprofile%\Appdata\LocalLow /t /setintegritylevel (OI)(CI)LRestart Outlook and check if it works.