We have been supporting multiple versions of the same software application being installed at the same time by changing the ProductCode. However, recently a new bug was found that we cannot install an older version of the software if a newer version is installed. We get the error message: "A newer version of this application is already installed on this computer. If you wish to install this version, please uninstall the newer version first. Click OK to exit the wizard."
I don't see why any of the versions are considered the same application since they have different ProductCode GUID values and even different UpgradeCode values. Does anyone know how to prevent this error from stopping the installations? A flexera community post refers to the ISPreventDowngrade property, but I don't really understand it and it feels irrelevant since we're essentially attempting to tell the machine that these different versions are totally unrelated.
The error you see is due to ISPrvent downgrade is configured to allow and sometime it will happen the product code is not changed,
You can use the msi diff tool to compare the 2 msi and you can make sure the upgrade code and product code are different
And also open the msi or ism of higher latest version and make sure ISpreventdowngrade is not configured to "Any earlier version" and the upgrade code option "Product sharing my upgrade code" is not using the upgrade code older msi versions upgrade.
