I had a very similar problem with my previous Arlo cameras connected to HomeKit. I had to remove all my Arlo cameras from the Homebase, reset all cameras and Homebase and re-add all cameras then add to HomeKit again, this worked for me, I could see all my cameras. Hope this helps. I have removed all my 2C cameras from HomeKit, the battery drain was terrible.
A little late here, but just had a similar problem with a Eufy indoor camera. Turns out to reset the camera you have to hold the sync button down until you hear two beeps, about 10 seconds. After that I was able to re-add to Eufy and home kit both. I cycled power, but apparently that is not the same as a reset.