Can't update any plugins

I, all of a sudden, can't update any plugins: "TypeError: Failed to fetch."

I was initially using Grav v1.6.30 but tried with all versions of grav through v1.7.14.

As per another ticket ( _Originally posted by @rhukster in https://github.com/getgrav/grav-plugin-admin/issues/1847#issuecomment-595800309_ ) I used every possible value (auto, fopen, cURL) for the Remote Fetch Method config.

This occurs in Chrome AND Firefox.

No file, test, or entry point is named. Start by reviewing the 23-comment thread and reproducing the plugin update failure in Chrome and Firefox across the listed Grav versions and Remote Fetch Method values. Done means the failure has an identified cause and a verified fix with regression coverage.

Written by the indexing model from the issue text.