The main factors to check:
- The title has been assigned the media type TV Serie, and the TV icon to the right of that assignment is blue and not red.
- The episodes have been mapped. Though sometimes this seems to be corrupt in MMCM, and you have to delete & re-add each disc and remap episodes.
- Review the CME log when exporting that title - it should export the mmSeries.xml and mmEpisode.xml files
- After corrections are made in MMCM, and you have re-exported in CME, do a Full Sync in CMC.
The title covers come from MMCM, so look there first to make sure they were successfully downloaded from the My Movies online service. If they are missing in MMCM, it is impossible to export them with CME.
If they are there in MMCM, then examine the CME log when exporting these titles to see what it says about these covers.