Sooner or later the remote control stops working. The remote control may have broken, for various reasons. It may happen that you have spilled something on the remote control or that you have dropped it repeatedly. If something is spilled on it, immediately wipe up as much liquid as possible. then remove the batteries and place the remote control in a bag or container of rice. Wait a few days and the rice should have absorbed the liquid.
If it has been dropped several times and broken, you usually need to buy a new one as it is difficult to repair a remote control. If the remote control is older, it can be difficult to get hold of. There are some dealers who offer used remote controls for air-to-air heat pumps. Otherwise, it may work with a universal remote control. Keep in mind that some of the previous functions may not work.
The best option is when the remote control stops working because the batteries have run out.
There are different models of remote controls, some have a battery cover on the back and others on the front. some are easy to unlatch but some are more difficult. These models have a stop before the door fully opens to reveal the batteries. Here you need to pull a little harder.
To check that it is the batteries that have run out, you can function test the remote control afterwards. By having the camera in front of you (if you have an android) and pressing a button on the remote control, you can see if it sends a signal or not.
On some models it is required that you restart, reset, the remote control. This should be in the manual or on the back of the control.