I don't know why older installer downgrade newer one. Maybe someone could help me. I have a product. Everytime with new version I'm changin Product Code and leave old Upgrade Code. I'm also increasing Product Version for example from 9.5.0.0 to 9.6.0.0. I have defined Major Upgrade which should upgrade any older version of product sharing my upgrade code.
In the effect: 1. When I'm installing newer on older it is working fine - the files are updated and everything works fine 2. If the same verion is run on installed product I get Maintanance mode. It is also Ok. 3. When I run older instance when newer is installed I get two instance of product. It is not OK! In normal mode I can handle it in script but I'm running this installation in silent mode and I cannot do anything in the script. How I can prevent of duplicating product?
By default IS creates ‘ISPreventDowngrade’ error custom action to prevent the downgrade. This CA should take care of downgrade. Perhaps check your upgrade code? Whether the two versions use the same upgrade code?
