To update from JoomGallery 3.3.4 or older to the new version, please note the following:
- Install the new version (JoomGallery 3.3.5 or later) via the Extension Manager of Joomla!
- In the control center of the JoomGallery you will be offered updates for the installed JoomGallery extensions. Now run the update for all already installed extensions of the JoomGallery.
- After all extensions of JoomGallery have been updated, go to the following menu item: Extensions->Manage->Update Sites and click on the button "Rebuild".
Thus, the update should work fine.