Just going through troubleshooting and isolation steps I would be doing if this was happening to me, this has me stumped. Please forgive me if some of it seems obvious or elementary.
Do you have any other copies of Motion saved anywhere else such as on another partition or TimeMachine back up when you updated? That might cause issues according to: Final Cut Pro X, Motion 5, Compressor 4: Issues updating via the Mac App Store - Apple Support
If you do have other copies, when you're launching Motion, are you launching the version located here /Application/Motion (navigate to your Applications folder and 2X click the Motion app) or are you launching it via another means? - Just verifying that the current version is actually getting launched.
When removing Motion, did you remove it by going to /Application/Motion and moving Motion to the Trash, or did you remove it from Launchpad by clicking and holding on the Motion icon until it shakes and then clicked the x ? - Removing it from launch pad doesn't remove it from your computer, it just removes the shortcut.