| Symptom | Likely Cause | Solution | |---------|--------------|----------| | “Widevine CDM not installed” | Corrupted or missing plugin | Go to about:addons → Plugins → check Widevine status; reinstall via Firefox settings. | | Video stuttering or black screen | Outdated version or GPU driver conflict | Update Firefox, update graphics drivers, or disable hardware acceleration. | | “License request failed” | Clock skew or network interference | Sync system time; disable VPN/proxy; clear site cookies. | | Widevine crashes on load | Corrupted local CDM files | Delete gmp-widevinecdm folder inside Firefox profile directory. |