If you are still having problems with Motion you can try to uninstall Motion completely. You have two options here:
If you successfully logged in with your license key and you are able to access the panel, you can go to the Menu > About > Uninstall. This action will remove all of the files and folders associated with Motion for you.
If you are not able to log in with your license key and you are encountering problems on the login screen, you can remove the following files:
C:\Program Files\Common Files\Adobe\CEP\extensions\com.mtmograph.motion-next
C:\Program Files(x86)\Common Files\Adobe\CEP\extensions\com.mtmograph.motion-next
When all the folders are removed, install Motion again with the latest installer. You can find the latest installer here.