Hello,
Indeed, the upgrade process fails when using the fourth field of the
ProductVersion. This is happening because the fourth field of the Product Version is ignored by Windows Installer when comparing product versions. This is why you should make sure the first three fields of your upgraded Product Version have an increased version than those of your old Product Version.
When the first three fields of the old and upgraded Product Version are identical, then the upgrade installation will either fail with
"Another version of this product is already installed" message or will be
installed side by side with the old version (when using different Product Codes).
However, you can still upgrade your application when using the fourth field. Please take a look on the
How do I remove the old version when using the fourth field of the Product Version? article with related information for hints and guidance.
If you have other questions, please let us know.
Best regards,
Dan