Read the service’s browser requirements
Use the genuine service page and its published support information. A stream working in VLC does not prove that the service’s website supports the same file or account in Firefox. A website needs its own appropriate browser delivery and controls.
Keep Firefox and the operating system current through their normal update routes. Avoid unverified extensions that promise to unlock protected streams or replace subscription requirements.
Understand the Widevine choice
Mozilla documents Google Widevine as a content-decryption module used for some DRM-controlled media. Firefox settings provide a user choice about DRM playback, and supported-platform details matter. It is a normal browser component decision, not a way to bypass content protection.
If the service reports a DRM-specific error, compare the browser’s current module/settings with Mozilla’s documentation and the service’s supported platforms. A playback error with no DRM context may require a different diagnosis.
Do not apply one Linux rule to every system
Mozilla’s documentation distinguishes supported 64-bit Linux from obsolete 32-bit Linux Widevine support. Record architecture alongside distribution and browser version when it matters. A general Linux label is not a complete compatibility record.
A Windows or Mac result is also not evidence of the same service’s Linux support. Keep the tested environment with every conclusion.
Preserve privacy during troubleshooting
Record the visible error, browser version and service page without exposing private account tokens. Clearing cookies or changing a browser profile can remove a sign-in session. Retain a recovery route and use the least disruptive check appropriate to the actual error.