I have asked the same question to Garmin Support, but I post it there too. Maybe someone has the same problem.
Some of the sync features between Connect (web-based) and my Instinct do not work. In particular:
1. Connect does not visualize the correct version of the Instinct and suggests me to update. In particular, Connect visualize v2.10 and suggest update to v2.60. However, on Garmin Express the version is 2.60 and no update is obviously possible.
2. Most important. I am unable to send a training created on Connect to my Instinct. On Connect, I have created the training and I have sent it to my Instinct. Garmin Express correctly opens up, says "completed syncronization" but I am not able to find any training into the Instinct.
Garmin Instinct, v2.60 (?)
Garmin Express 6.9.0
Mac OSX 10.12.6
Web based Garmin Connect