Paste the complete HTTPS M3U8 URL into the HLS tester and start playback. If the manifest loads, inspect available levels, resolution and codec data. If it fails, check the diagnostic log for network, manifest, media, 403, 404, CORS or mixed-content clues.
Practical advice
Use the original source file or URL whenever possible, keep a backup before conversion, and treat browser error messages as troubleshooting signals rather than proof of a specific server-side configuration.