Warning: Failed to download action ... Error: Response status code does not indicate success: 429 (Too Many Requests).

[jsoref]

runner/src/Runner.Worker/ActionManager.cs

Line 1191 in 1b5486a

executionContext.Warning($"Failed to download action '{downloadUrl}'. Error: {ex.Message} {requestId}");

I'm not sure where the other half comes from, my guess is:
https://github.com/dotnet/runtime/blob/4a0b333e80a29ea29a8256285f8a01a54283b5ef/src/libraries/System.Net.Http/src/Resources/Strings.resx#L211

This error happens periodically (there are tickets here that reference it; we tripped on it during one of the many actions outages today).

The message isn't great. The response is to try again later, which isn't entirely wrong, but the message could use some love on all sides.