Description

When the Experience Editor is started from the Launchpad it shows the website that the user was logged in to. But when the Experience Editor is started from the Desktop it shows the site defined in the Preview.DefaultSite setting. If the user does not have permission to preview the default website, an error message is displayed.

Solution

To resolve this issue, download and apply the appropriate patch available on this page:
https://github.com/SitecoreSupport/Sitecore.Support.119280/releases

To get a solution for other Sitecore XP releases, contact Sitecore Support.