Today we experienced long waiting times for Windows + macOS machines.
The issue was caused by a server issue, where memory issues were causing restarts of our hub (hub.testingbot.com)
This in turn caused the machines running the tests to fail to communicate with the hub, causing tests from clients to wait up to 5 minutes before a test could start.
If your test runner is configured with a http connect timeout < 5 minutes, this may have caused issues where tests would fail to start.
The memory issue was resolved and we are looking into a solution to prevent this from happening again.