Linux users where there is no default snapd daemon get the problem. There is no necessary path /var/lib/snapd/desktop/ in the variable XDG_DATA_DIRS for the first account.
https://sourceforge.net/p/docfetcher/discussion/702424/thread/493d5c05b2/#610b
The “restart” step after installing snapd and before installing the snap, that was mentioned in the forum you linked to, is important precisely because restarting allows your environment to be set up properly.