DIAGNOSIS: The IR (infrared) sensor on the fan is either blocked, or there's a pairing/sync issue. Less likely, but possible, is a dead sensor on the fan unit itself.
FIX: First, check the obvious: make sure you're pointing the remote directly at the IR receiver window on the fan's control panel, not the blades or the tower body. Clean that little dark plastic window with a dry cloth—dust can block the signal. The most common fix for a totally unresponsive remote is a hard reset of the fan. Unplug the fan from power for a full 60 seconds, then plug it back in. This often reinitializes the receiver. Try the remote again.
IF THAT DIDN'T WORK: Try using your phone's camera to test the remote. Point the remote at your phone camera and press a button while looking at the screen. If you see a faint purple light from the remote's LED, it's transmitting. If you don't see light, the remote is definitely dead. If you do see light but the fan still doesn't respond, the IR receiver on the fan is likely faulty.
HEADS UP: These fans don't "pair" like Bluetooth; it's standard IR. Any universal IR remote that can learn codes might be able to control it if your original is toast, but it's a hassle to set up.