When you try to upgrade Management Packs to the latest version, sometimes the install button is greyed out. This Article helps understand why.
When you are upgrading your Management Packs to the latest version, the natural thing to do is to select all the Management Packs and click "open" like in the screenshot.
Then when you want to click the install button you notice that it is greyed out.
The issue here is that while you have selected Management Packs with a higher version, you have also selected Management Packs which have the same version as the current one installed. SCOM will not tell you which Management pack has the same version as the previous, so you will have to remove the Management Pack for which you think have the same version as the current one installed. Once you removed all the Management Packs with the same version from the install list, the install button will become available again.