Colibri Page Builder stuck on “Loading… Please wait”

As the subject suggests, I’ve purchased the Lifetime Pro version of the Colibri WP theme. But I cannot customize it because the required PageBuilder plugin just hangs on “Loading. Please wait” with a spinning circle.

Things I’ve tried:

• Deleting and reinstalling the plugin
• Deactivating all other plugins
• Using the free non-pro PageBuilder as a test
• Using a different browser with no previous cache or cookies

I’m at a loss for what else I could possibly do here, but it seems this non-functioning plugin is required to edit the theme, which is a real show-stopper.

I’ve opened a support ticket hours ago, but have yet to receive a response. Please someone help.