I notice that splits no longer display on Garmin Connect for any activities after about 17th Feb. I did a search on the GC forum and found a known issue with the following explanation:
Garmin is aware of an issue where split times are not displaying when comparing activities. We apologize for the inconvenience and the Garmin Connect team is working on getting this issue fixed. We appreciate your patience and this post will be updated as more information becomes available.
The above was posted by Garmin on 21st Feb, so they have been aware of the issue for over 2 months and the issues has not been corrected nor have they posted any updates. This suggests that they have done nothing. It shouldn't be that hard considering it was a feature that once worked. They just need to figure out what change broke it and then roll it back.
While I have been really happy with my 310xt, Garmin's customer service sucks big time.