Identify the audio arrangement first
Amazon’s general Fire TV sync article directs Home Theater setups to Lip Sync Tuning rather than the ordinary AV Sync Slider. A common complaint such as late dialogue does not make the two setup routes identical.
Write down whether audio comes from the television, a receiver, Bluetooth headphones or a configured Amazon Home Cinema arrangement. That single distinction determines which official instructions should be used.
Keep correction on the intended layer
Amazon’s dedicated Home Cinema article gives Settings, Display & Audio, Alexa Home Cinema, then Lip Sync Tuning. Its US Home Theater version uses Display & Sounds and Alexa Home Theater. Follow the labels shown on your supported device and the on-screen tuning instructions. Keep the original setting in your notes before making an adjustment.
Compare a short familiar dialogue passage using the same speakers. If another speaker is audible at the same time, distinguish an echo between outputs from a single output being late against the picture. Those observations need different evidence.
Avoid accumulating offsets
Leave unrelated app and receiver delay controls unchanged during the comparison. Otherwise a good-looking result might depend on several opposing corrections, making later troubleshooting harder.
If the expected tool is unavailable, report the exact Fire TV and Home Cinema hardware and current menu. This documentation-based distinction does not promise that every model supports the same home-audio features.
Questions answered
Are Home Cinema Lip Sync and the ordinary AV Sync Slider interchangeable?
Amazon directs Home Theater users to its separate Lip Sync Tuning route.
Does a missing slider prove the app failed?
No. Tool availability and the selected hardware route need checking first.
Sources & further reading
Official references for the subjects discussed. Service terms and device software can change.