During a network upgrade we experienced intermediate connectivity issues between our Selenium Grid and VMs between 17:00 and 18:30 UTC today.
A misconfiguration caused some VMs to no longer respond to network calls. Over time this resulted in a cascade of events, causing most tests not to run on our VMs.
We reverted the change, but it took a while to get the grid back to a stable state.
During this time, VMs were able to run your tests, but tests failed because of lack of public internet connectivity on the VMs.