Firstly, make sure that your mInstaller app is updated to the newest version. After the app is updated, uninstall the product and install it again. Now check, if you can see your product in mInstaller. If not, follow the below instructions:
Corrupted macOS disk permissions may prevent mInstaller from properly finalizing the installation.
To fix them, please try the following:
Close all applications running in the background (especially Motion and FCP), otherwise the files and folders that are in use will be omitted,
Open mInstaller and uninstall the affected product,
Go to mInstaller Settings via the Cogwheel Menu, [Repair] your Disk Permissions and [Clear] mInstaller's preferences (do not log back in onto the app just yet),
Open the Disk Utility (you'll find it in your Applications > Utilities folder), select your disk in the menu on the left side of the app's screen, and press “First Aid”,
Select the partition below your disk, press First Aid again and, once the process has been finalized, close the Disk Utility,
Next, reboot your Mac, log onto mInstaller, install the previously uninstalled plugin and check if it helped.