Right, have you followed these instructions? Remember, MyTracker needs to be installed like MyBB, you can't just activate the plugin. (This will be sorted in the next Snapshot).
- Upload the contents of the download to your MyBB folder. Remember to keep the structure of the download intact!
- Rename the ./tracker/ folder to whatever you want to call it, then go to the install folder in your browser. For example,
myforum/tracker/install/ if you haven't renamed the folder.
- Follow the installer process, then activate the plugin in your ACP.