For some time now, I have been getting the message when updating the extension:
Update: The update source #7 “Gantry 5” could not be opened - URL:
updates.gantry.org/5.0/joomla/pkg_gantry5.xml
If the Joomla Updater fails you can always download the current versions for things here and manually update:
gantry.org/downloads
SEARCH the forum first! These boards are rich in knowledge and vast in topics. This includes searching just the 'Solved' forums, using Google, and using ChatGPT