Cees_Ping
I am sorry about the trouble. Unfortunately, this will not be resolved with a Garmin Express update as this is not an issue with Garmin Express. Something was changed in OS X 10.11 that prevents the device's storage from mounting so it will not even display as a drive on the computer. We have created a case and are currently investigating this issue.
Jason
Just to let you know that Garmin Express running on OS X 10.11 does not recognize (mount) a nüvi 2797 either.