Arlo light does not turn on manually
I had exactly the same issue. I have 2 Arlo lights. After getting them set up, one of them decided not to turn on when I toggled the manual switch on my iPhone. After reading someone else's suggestion here on this board, I removed the rogue light and re-added it. It worked for a few minutes but stopped responding again. All this time the motion sensing and everything else was working properly.
I managed to get the light to work by simply unplugging the Arlo Bridge from the outlet and replugging it after one minute. This is the old reboot concept when every other logical method fails 🤣. This method worked for me and I hope it can resolve your issue as well. 🤞