The symptom and its scope
The title must contain a subtitle track or provide a compatible external track, and the player must render it. A missing track cannot be created by changing subtitle size.
Inspect the available tracks, select the intended language and compare a second title. Use a timing offset only when a supplied track is consistently shifted.
Separate a source issue from a setup issue
If one source fails while another plays, record the exact affected channel or title and its selected quality. If every source fails, confirm the profile, account expiry and active-connection allowance through support. If one device differs from another, capture the player build and device model before changing the account.
A wired comparison changes the network path while a decoder comparison changes local playback. Keep those tests separate. Use the linked diagnostic articles to choose one controlled comparison instead of applying several resets at once.
Before a destructive reset
Keep a working profile and record the app version. Clearing app data can remove playlists, favourites and guide preferences. A factory reset removes more than the symptom you are testing and is not an appropriate first response to a single-source failure.
The support report
State “subtitles are missing or out of sync”, the device model, app version, network type, account method, source, time and timezone. Include what still works and what changed during the test. Redact passwords, private playlist URLs, service codes, device keys and customer information.