Nine times out of ten this is batteries, line-of-sight, or a mode-lock you didn't know the remote had. The unit itself is almost never the problem - and there's a manual override button on most indoor units so you're never locked out entirely.
Safe checks first
- Fresh batteries, correctly seated. Weak batteries produce the most confusing failure mode: the remote's screen works but the transmit LED is too weak to reach the unit. Replace both, don't mix old and new.
- Test the transmitter. Point a phone camera at the remote's emitter and press a button - most cameras show the IR flash on screen. Flash present = remote fine, look at the unit side. No flash = remote (or its batteries).
- Line of sight and distance. IR needs a clear path to the receiver window on the indoor unit - decor, curtains, or standing off-angle at range can drop commands. Bright sunlight on the receiver also drowns IR.
- Check for CP / child-lock / hold modes. A CP display means the unit was switched off by remote control lock on many models; remotes also have hold/lock combos (often two buttons pressed together) engaged by pocket presses. Your model page links the manual.
- The manual button. Under the indoor unit's front panel there's a small AUTO/manual switch - it runs the unit without any remote and proves the unit itself responds.
- Wi-Fi app as a bridge. If your unit has app control, use it while sorting the remote - and note that a working app + dead remote definitively clears the unit's receiver only if the receiver is separate; a technician can test that.
Beyond the safe checks (technician scope)
A confirmed-transmitting remote plus an unresponsive unit (manual button works, IR ignored) points at the receiver/display board - a small, inexpensive part, but panel-off work. Display-board communication codes (EH 0B class) confirm it - check the library.
Sources
No model-specific systems are linked from this guide yet.