This problem can be caused by a few variables but it's very easy to fix. Simply change the extension of the downloaded file from .tsi.html to .tsi and Traktor should be able to import it as expected. In the event that renaming the file doesn't solve the problem try using a different browser and download it once again.
If you find any mapping with this problem please notify us and we'll re-upload a fixed version. We encourage users to upload their mappings as a compressed files (zip or far) to prevent this problem.