Home Assistant App recently started throwing cert errors with no cert involved

I started using the mobile app and love it. I only use it locally, and no tunnel is involved.

Lately (and only lately - like last month or so) it has begun giving fairly continuous certificate mismatch errors, takes me to settings, where I go back and everything keeps working. It is not failing to work, just giving the error.

This is episodic – it will happen nearly continually for a while, then stop completely. I have not found a pattern. As i write this I can’t reproduce it.

I do NOT use certificates. I do NOT use Nabu Casa for remote access (if I do, I do use a tunnel, and the darn app is flakey with it, but that’s a different story).

Below is the server setup, notice the HTTP.

In the HA configuration.yaml I have an internal URL and no external URL, and the internal URL is identical (and without http).

This APPEARS to have started with the companion app starting to ask for permission to tell when I’m home and away (I did not give it permission as I want it to always think I am home and using the local subnet).

DNS, mDNS, and Wifi connectivity is really good - my 2700sf house is covered with 5 different access points. I have done networking for a living for decades; nothing is actually broken in the network.

I suspect this is caused by me not allowing the companion app to do remote access using nabu casu, but I absolutely prefer to do my own network security where I can. I just want it to be simple – take the server address and access it. Not try to “help” me navigate remote access. Especially if I’m not remote, and this posting is all about local access.

Am I missing something here? Or did some recent update break it?

Linwood

PS. It would be quite helpful if the error message actually told WHAT certificate is mis-matched, since I have no clue – not using a certificate as best I can tell.

Well, I found an amazingly simple fix for this.

Just post the question.

It has not happened one time since I posted this. It was happening several times a day before that.

I have no explanation. There was a playstore update to the tool on 1/31/2026, I don’t know when it auto-installed for me. Maybe that fixed it. The release notes are so cluttered with “bump this version” Im not sure if there is anything in there relevant, though there is a “hang on lan with no internet”. Though i wasn’t having hangs, and I have internet.

Arggg… almost as though it was reading my posts, yesterday for about 2 hours it just continually gave the errors again. Example below.

I can just hit “settings”, then exit from settings (no change) and it would work, until the next time I started the app.

WHAT CERTIFICATE? I’m not using any certificates (or https) overtly so what is not matching? It’s so silly it gives an ALMOST useful message, but no details, no longs (that I know of?), nothing.

Sigh… anyone know… WHAT CERTIFICATE does it use?

With some assistance from Timo on discord, I have this figured out.

The error is originating when the google cast integration’s media player is trying to display a cover image from plex.

On my network nothing uses https, including plex, it’s all http and all local subnet not remote.

When the media player tries to get a cover image (presumably from a url somehow derived from the plex server’s connection to the google TV 4k Streamer), it gets a https url. The actual connection is http (or it wouldn’t work). Something is changing the cover image (only) to https:

That URL is the plex server not the HA server. This is from a browser viewed in debug, the browser ignores the error showing a no-image image.

Instead of just ignoring the error Home Assistant companion is showing the modal error popup. Which is fine (if overkill), the real error is the https itself.

I’ve bugged it here (it’s not a huge issue, but it’s confusing enough fixing it would save people chasing their tails, as I have done):

https://github.com/home-assistant/core/issues/163573