I just had this happen to me. Purchased a new TV (that is in my RV) and the remote control was not working. I didn’t have batteries readily available to swap out. The remote control was an infrared remote control and with an infrared remote control, you can not see the light through the infrared blaster lens with the naked eye (when the power button is pushed).
The main technology used in home remote controls is infrared (IR) light. The signal between a remote control handset and the device it controls consists of pulses of infrared light, which is invisible to the human eye, but can be seen through a digital camera, video camera or a phone camera. [source: Wikipedia]
I remembered a trick I read where you can take your smartphone camera, turn it to the rear-facing “selfie” view, point the remote to the “selfie” screen (about arms length away) and push a button on the remote (like the “power” button) and you should see a light flicker (on the smartphone screen). I did this and did not see any light flicker, confirming there was an issue with the remote. When I got home, where I had batteries, I tried the same trick with the smartphone; and, guess what I could see the light shine and flicker in my smartphone’s camera “selfie” screen (confirming the remote was now operational). I further confirmed the operation of the remote with the TV when I returned to my RV.
So, if you ever need to troubleshoot your infrared remote control, give this trick a try. It does work…