Identify the screen before blaming the stream
Start Trex IPTV remote checks by noting whether you are on the Fire TV home screen, a player menu or the video itself. Amazon distinguishes the system Home action from directional navigation and selecting a focused item. A direction button can move a menu highlight without starting playback. Record which button you pressed and what changed. Trex IPTV 8K is the service you are asking about; that does not establish which player or remote model is installed.
Compare system navigation with the player
If appropriate, press Home once and see whether Fire TV returns to its home screen. This may interrupt viewing. Check whether the directional buttons can highlight another ordinary menu item. If system navigation responds but a player action does not, describe that difference rather than declaring the whole service down. If nothing responds, follow the current manufacturer instructions for your exact remote and device. Do not copy an unfamiliar reset or pairing sequence from another model.
Give support a precise control report
Note device and remote models, system and player versions, the screen, button and observed response. A visible selection highlight and a failed video command are different observations. Keep the report free of passwords and private playlist links. Avoid buying another plan because one control seems inactive. If support asks you to compare another device, close the existing stream first: Trex has one simultaneous connection. These checks narrow the question; they do not prove the remote, app or service is faulty.