AE, OS and workflow details would help diagnose the problem. Just saying it stopped working does not give us much to go on.
Im kind of new to AE and the forums... usually it all worked without issues.
Running the Newest versions of Adobe ( Creative cloud )
OS X el Capitan 10.11.5
Not sure what you mean by WorkFlow Details
Hello. Welcome to After Effects.
Saying "newest version" isn't ideal. We had someone saying that when they were running CS6! Also, the CC app sometimes lies when it says you're updated. So, please, tell us exact version number down to the build number. The actual latest as of this writing is 220.127.116.11.
The rest of the workflow details would be things like length of clip you're trying to track, exactly what steps you're taking to track it, codec and format of the footage, etc.
This page should give you some ideas of other useful info.