Some useful troubleshooting steps when you cannot remove or install an updated Outlook addin –
1. Run the installer from the command line calling the /lv switch to enable logging and review the log for clues.
example – msiexec /i “c:\msitest\installer.msi” /qn /lv “c:\msitest\installer.log”
(replace ‘installer’ with the relevant installer name)
2. Fix problems with the Microsoft ‘Fix it’ tool
3. Another way (older method) would be to use the cleanup utility MsiZap.exe supplied in the Windows SDK