Mozilla backpack will close soon and, once the service will shut down, users using Mozilla as default backpack won't be able to use the backpack (connect, send badges and display them in the user profiles), unless they set the default backpack to Badgr.io as described in https://docs.moodle.org/37/en/Badges_settings#Enabling_Badgr_as_the_active_external_backpack.

Until the Mozilla service shut down, this could be reproduced using https://backpack.openbadges.org.badgr.io/ instead of https://backpack.openbadges.org.

This information in Moodle 3.7 is stored in the {badge_external_backpack} table.

For Moodle 3.6 onwards, the behaviour is the expected (so the patch for fixing this, should be only applied to 3.7)