I was trying to add a new device to HomeKit. It kept failing to connect. I got the error “Unable to Add Accessory“, even after following the manufacturer instructions multiple times to reset, reboot, and use a 2.4 GHz network.

Multiple people are having this problem, with multiple accessories from different manufacturers. As an example, see this reddit thread (one of several).
After several hours of troubleshooting, I finally got the accessory added into HomeKit. Here’s what I did:
- Reset new HomeKit accessory (in my case an Eve Light Strip, partly manufactured by Taiwanese Dexatec/Ennoconn), unplug for 3 minutes, plug back in
- Reboot phone
- Go to Eero > Discover > HomeKit and completely disable HomeKit Secure Router (just disabling HomeKit security in the Home app doesn’t work). All my accessories remained and I didn’t have to setup anything new
- Unplug all HomeKit hubs in the house except for one
- Go to Eero > Settings > Troubleshooting > My Device Won’t Connect > Enable 2.4 GHz for 15 minutes
- Try adding the device into HomeKit again (still within the 15 minute 2.4GHz period)
- Go back to Eero > Discover > HomeKit and enable HomeKit Secure Router again
Since HomeKit Secure Routers are a WPA2 feature and Apple hasn’t updated it for WPA3 as of this writing, it’s possible Eero and Linksys are deprecating support for it.
I’ve since added an additional device, a smart plug (from Eve no less), with HomeKit Secure Router enabled, so hopefully I won’t have to go through this process every time I want to add a new accessory.
For anyone wondering what I did with the Eve Light Strip, I took inspiration from Eve’s product photo (below) and put it behind my headboard. It works great now that it’s added to HomeKit. Now I have dimmable adaptive lighting in bed without the glare/brightness of the overhead light for late night reading. It might also be possible to wake up gradually to adaptive lighting but I haven’t researched that yet.
