Similar to this issue from Fabrice Benhamouda the Trello boards in my organization have had all of their GitHub Power Ups cease functioning in the middle of last week. Unlike him, the situation has not solved itself.
In some instances, the button where the Power Up would normally be exists will load, but is blank. In other situations the buttons in the Power Up region do not appear to load at all in a card. In both situations I see the following error in the browser's JS console:
GET https://github.trello.services/github.e819f7fc.js net::ERR_ABORTED 404
This references "index.html:1"
Followed much later by
Error, timeout while initializing index iframe for https://github.trello.services/index.html?ver=06487f4b1cd0. Timeout=30000ms
This message references "instrument.js:110".
Here is a screenshot showing the GitHub Power Up missing, and there being an a blank button where it normally would be.

This has been checked on the most recent two versions of Mozilla Firefox and Google Chrome. Plugins were disabled, caches were cleared, log-outs-and-log-ins were performed. None of these actions have resolved the issue.
Even stranger: when I navigate to the Power Up setting itself, two issues arise which seem similar. Selecting "Edit Power-Up Settings" under GitHub from the Board Menu does nothing (was patient, many attempts made). I can navigate to the Power Up info, i.e. "Board Menu > GitHub > View Power-Up", and the GitHub plugin appears with the basic introductory information about the Power Up. However, clicking on the "Settings" button (right below "GitHub - Trello Inc"), no options in the resulting menu perform any actions.
My team has made extensive use of this Power Up since its inception, and I have not seen an issue of this nature before, to say nothing one stretching on for many days.
Other Trello users: Is anyone else experiencing this issue? I do not seem to be alone. As two other people here seem to share the situation through the moment of writing. It would be useful to learn who else is having similar issues.
Atlassian and/or Trello teams: Please advise.
Regards,
Paul