You filename format is invalid, it’s mixed.
See this topic for details for formats recognized by MCEBuddy: Metadata matching, extraction, renaming from files and downloading from the Internet
It should be either SHOWNAME_IMDBID or SHOWNAME.SxxEyy.SUBTITLE
Your filename seems to match the second pattern so it’s taking the subtitle as the IMDBID
Title: Mission Impossible
SubTitle: tt0649283
Description:
Network:
Network Affiliate:
Parental Rating:
Media Credits:
Genres:
Season: 6
Episode: 15
Since there is already a subtitle present, MCEBuddy won’t overwrite it from the internet. In the next version of MCEBuddy we’ll give an option to overwrite the metadata from the internet (e.g. TVDB, TMDB etc).
For now you should change your filename format to match either of the two formats above. If you want it to use the IMDBID then remove the SxxExx from the filename and it’ll download the details directly for that IMDBID.