Possible reason: You have disabled iSlide add-in so that it cannot load automatically.
Solution
Plan A: (Optional) Find the COM Add-in and then remove iSlide Add-in
Plan B: Reinstall the latest version of iSlide add-in
Prev Page Why is it still the old version after update?
Next Page COM Add-in shows that iSlide Tools has been "Uninstalled". COM Add-in was disabled.