Application credentials for nest was added in 2022.7.
I’m not sure what you’re trying to do exactly or where you’re stuck, but i recommend running the latest version of home assistant and following the nest integration instructions on the home assistant site. They have extensive troubleshooting information for all common misconfigurations.
I had to create upgrade to 2022.7 via docker as the upgrade process in HA was not working for a core image alternative. I will work on Nest now… Thanks
I have been round and round with this and just keep getting Can’t link to (projectID)
Please contact (projectID) if the issue persists from nestservices.google.com/partnerconnections.
I have been through this 10 times now and it just isn’t working for some reason. I have created new projects and credentials and device projects but i’m just not getting it.
Nest works BUT 2022.7 broke connection to Synology NAS… I will check to see if anyone having issues with NAS integration on 2002.7
See Nest - Home Assistant with the section under Can’t link.
Most likely you need to read the bit about Application Credentials. This morning I updated with an additional screenshot to go along with the existing text about since that is something new that many people see and skip over, or don’t click through, etc. so hopefully that helps.
Deleting the existing credentials and starting over did the trick. Thanks for your support!
Well, as some posted, the integration changed, and I did notice that, so I’ve started all over from the top.
Created new Google project, added API’s, created consent screen, created OAuth, created new device access with the OAuth, but I still get a message that it can’t contact the Device Access Project.
This is very odd.
Check out the troubleshooting section in the docs and if your error isn’t there let me know
Ok, so I found out that I had some old stored credentials, I got rid of that.
Then I went through the setup again, and now I just see this popup after entering the Oauth:
Client ID and secret:
I don’t see anything in the logfiles.
I’m configuring it through the Nabu Casa URL, I fear that it gets confused because I also have a local name configured, with a let’s encrypt public certificate on it.
Oh darned, I found some old stuff in the configuration.yaml also, a link to a nest.yaml holding old credentials.
So after removing that as well, it linked up!
The steps are listed here:
Just had to search some more for the old (bad) credentials.
I’m having the exact same problems trying to convert my Nest link from desktop to web auth: specifically, both the blank dialog box and the “Can’t link to Home Assistant - Please contact Home Assistant if the issue persists” error.
I’ve already deleted my credentials from my config files and even deleted and recreated the Oauth creds and device access project. Here’s something really weird about that.
The page where I get the “Can’t link to Home Assistant” error has a URL like this: https://nestservices.google.com/partnerconnections/37df046c-aaaa-bbbb-cccc-9a49e0e8b4cd/auth?response_type=code&client_id=1234567...
I’m 90% sure that that client id is the old Oauth client id that I already deleted and was never associated with the new device access console project. This suggests to me that Home Assistant still has that information cached somewhere, but it’s not in the config files and I’m not sure where else it would be.
Ah, success at last! I was right, there is an application_credentials file in a hidden .storage directory. Deleting that file, restarting HASS, and then restarting the Nest integration finally worked!
I have no idea what that .storage directory is, if it’s supposed to be accessible via the UI, or if it exists by design 
It seems there’s at least two bugs here:
See the troubleshooting instructions which has details on the “Can’t link” error: Nest - Home Assistant
Yes, it is accessible via the UI: Application Credentials - Home Assistant
We definitely we don’t want to recommend people delete the storage files as it can impact other integrations!
As for your great suggestions:
Agreed, not working as intended, that should never happen. But I need more detail, Maybe having details from browser Developer console network tabs an help us figure out whats going? e.g. maybe an error payload in a browser response. on or turning up debug logging following the integration setup? Can we file a real github issue and fill out the template which asks for more details?
I sent a fix last week to prompt on deletion https://github.com/home-assistant/frontend/pull/13159 – there are valid use cases for preserving them, but the main point is providing more transparency and control.
Thanks, TIL you can manage application credentials separately from integrations 
No errors were returned in the developers console / network console, though I wish I add captured the actual request and response. I’m hesitant to risk breaking a working integration to capture debugging info, but I’ll consider it.
Yes, the app credentials are new in 2022.6 so expected that you haven’t heard about it yet.
I’m having a little trouble understanding your case compared to the previous report. In the previous case, they cleared out the credentials then saw the blank error message. In your case, i just see the can’t link error which is resolved by clearing credentials. Did you also see the blank error dialog? and when?
Yes I saw the blank dialog too. There’s a little more context in Nest integration presents blank dialog . Sorry, it was quite a long process of debugging and I encountered various errors.
As I recall, at some point I got the “can’t link” error. I discovered stored credentials in configuration.yaml and secrets.yaml and wiped those. Then I started getting the blank dialog box. Then trying again a day later (without changing anything on my end) it went back to the “can’t link” error. Finally clearing the stored application credentials fixed it.
Got it. Next person that hits this, file a github issue and we’ll talk there. It’s a bug, so it should be sent to developers so we can save the community from diagnosing.
@firsbe Can you make Nest - Home Assistant part of the solution here since it has all the correct steps listed?
Also we now have Finally! A WORKING NEST Integration with Home Assistant using Oauth! - YouTube for folks who are setting up from scratch.
Hi @allenporter
Well I caught the post, even though it’s @fribse 
Do you want me to try and update the docs, or post the steps in this thread?
Reall. Kudos here!!
I have looked for so long for this answer. I have had Nest Doorbel integration working, then Google changed their security I I kept messing around. Dozens of times redid all on Google Cloud. No sigar.
Till I found this post… so for those who had it working, but fail when reconfiguring:
!!! Remove the Application Credentials in the right top for Nest on the Integrations page !!!
Now Google can connect my account to HA and Nest is working. Finally. Thx!