: Many users find that the Firefox version of Video DownloadHelper is more powerful than the Chrome version due to fewer browser-level restrictions.

If you see the error, work through this checklist:

The browser extension cannot aggregate separate tracks into an .mp4 file without the CoApp. "Download Failed" for Last Month on Chrome #960 - GitHub

The “sadly we failed” message is frustrating because it gives no technical detail. But once you understand it’s usually a segment-streaming or DRM issue, you can decide whether to troubleshoot or move on.