I have a Tapo S505D dimmer switch installed, which supports Matter and WiFi. I don't yet have a Matter controller (I have an HE C-7), nor do I have enough Matter devices to justify buying one just yet. I've connected the switch to my WiFi network and have it working through the Tapo app and Google Home. However the switch isn't detected through either the Kasa or Tapo integrations.
Has anyone had any luck getting this switch integrated over WiFi?
Do you have "Third-Party Compatibility" turned on in the Tapo app, under your account photo/name (top left) > Third-Party Services?
That being said...
Yes, you do. 
See: How to use Matter on Hubitat Elevation | Hubitat Documentation.
Hi there, thanks for the response! I do have "Third-Party Compatibility" enabled in the app, which I did to get several Kasa devices integrated successfully.
Yes, since posting, I've been reading, and it seems like I was a bit confused about Matter and what the C-7 can and cannot do. 
Apparently it is not a Thread border router, but it can do Matter over WiFi, which is apparently what the switch is using.
From what I've been reading, I guess I need to add it to Google Home via Matter before I can add it to HE? I have a Nest Mini which is apparently capable of acting as a Matter hub... working on figuring all of this out now.
No, but if you do have another Matter controller and can do that, I'd suggest it. But as noted in the documentation, you can also use the Hubitat mobile app to commission and pair it directly to Hubitat with nothing else needed.
I was able to add it to Google Home using Matter, and I followed the instructions to link a new app or service. I copied that code into HE, and the screen flashes and brings me back to the setup code page without adding anything. I also removed it from Google Home and tried adding it directly via the HE mobile app, and it seems to find the device, but then it gets stuck on the step where it says "Pairing Matter Device - Current Step: Searching for Device."
Any ideas?
The instructions here probably need to be updated for the new version of GH. After tapping "Link apps & Services" I get a list of apps to share with. Instead of clicking an app, I hit "code" and used that code in the HE web interface.
And I would prefer to add it to GH first since I do use Google's voice assistants in my house and on my phone.
Not sure, but sometimes waiting a bit and trying again will help. You could also reset and re-pair (or technically re-commission and re-pair) the device, which might be necessary if you got far enough the firs ttime for it to fail. Check Matter Details on your hub too and remove the device if there's a failed pairing.
I've seen some networks have problems with Matter if they don't handle mDNS or maybe IPv6 well, both of which Matter relies on, but this should only be an issue with very old equipment (you don't actually need IPv6 enabled, and I'm not sure your equipment even needs to "know" anything about it) or if you have multiple networks set up (different vLANs, some mesh networks, etc.).
I just reset and re-paired through GH, which worked immediately. Then, here is the process I followed in the web interface. When I click "Start pairing," the screen briefly changes to the pairing screen and then redirects back to setup page.
Forgive me, I'm very new to HE. Where might I find the Matter setup logs?
Also, my network is fairly straightforward. I used my 2.4 GHz network when pairing to GH. No VLans or mesh to speak of.
"Matter setup logs" aren't really a thing, but the most revealing things tend to be the status on that screen. Regular hub logs are also helpful in general, though I don't recall there being much there for Matter specifically.
It sounds like all works well on the Google side for you? If I'm misunderstanding anything there, I'd definitely make sure that works. If you're just having a problem pairing it to Hubitat, it looks like you're doing it right. A hub reboot might help, as might removing any device that might happen to have been added to the Matter Details table if you got that far (probably not, but worth checking out!).
Matter is still pretty new, so unfortunately, every once in a while you might find some quirks like this. Hopefully, some combination of patience, resetting, and trying again might help! If not, you might want to see if the Tapo integration finds the device if you look again, or if any logs from that app might offer any clues.
Many thanks for your very helpful responses.
I think I've uncovered the root cause. Going to the Matter Details table reveals that the Matter Status is stuck on "starting." Similar behavior to what I'm experiencing was discussed in this thread, and the OP never posted a follow-up to say they had got it working. I've tried rebooting the hub and it is running the latest platform update (2.4.3.173).
Maybe it will decide to start up overnight? 
I'll try again in the morning and report back. Thanks again!
Odd, but that would probably do it! Does disabling and reenabling Matter on that page help?
I tried that to no avail, unfortunately. Maybe it's a bad radio? FWIW, although it's an older generation model, I bought it new/unopened just a few weeks ago. It's also worth noting that there is nothing showing next to "Fabric ID"
It looks like I'm back to where I started, getting the switch integrated over WiFi 
Since we are back at the beginning, yes the community Tapo Integration designed to work with the S505D. I verified that all HW versions (there are 4) at latest firmware version protocol and encryption methodology are consistent with the community integration. (I do not personally verify every Model, HW Version, and Firmware Version of all Tapo Devices. Comes to money and time.)
Some Items if you have problems with Wifi installation:
For the S505D, I beleive you can likely bypass the Google Home and install as follows:
I have tested this on my Tapo and Kasa Matter Plugs - all work. My bulbs do not work since my specific HW/Firmware versions do not support ble_whole_setup
Sent PM.
Just an update for anyone who comes across this in the future. Many thanks to @djgutheinz for his support in helping me troubleshoot this. Turns out, even though I had enabled "Third-Party Compatibility," that setting had not been pushed down to the switch. The logs showed that the device was discovered, but was unresponsive (timed out) when HE tried to contact it.
The fix: disable Third-Party compatibility, wait a while (I waited 10 minutes) and then re-enable it. We learned that this can take a lot longer than you'd expect. In my case, it was not working an hour or two after changing the setting, but it did start working later that same day with no further changes being made. This tells me that it can take several hours for the setting to get pushed down to the devices.
Also, if you can get the switch working via Matter (another problem entirely), then that is definitely the preferred method.
Glad there's a resolution, so you can use your switch. We still need to figure out why Matter is stuck in a state of "starting" on your hub. Hopefully that will be resolved in your other thread. I am marking this one as solved and closing it.
Download the Hubitat app
