Click Add to table and then Update and Save and continue.
In the test users area, click Add users and add your Google email, Use the same email as the currently logged in account.
Click Save and continue.
Go to Left menu > APIs and services > Credentials and click Create credentials, select OAuth client ID.
As Application type select Web application. Enter any name you want.
In Authorized redirect URI enter the redirect URL, get it from ChatBot > Settings > Artificial Intelligence > Google > Authorized redirect URI.
Click Create.
Copy Client ID and Client Secret and paste them into ChatBot > Settings > Artificial Intelligence > Dialogflow.
Save the settings.
In Settings > APIs & Services > OAuth Consent Screen click PUBLISH APP.
There is no need to complete the review process, leave it in the pending review state.
Click ChatBot > Settings > Artificial Intelligence > Google > Synchronize.
Login with the same Google account you have used till now. On the next screen click Continue.
On the next screen select all scopes and click Continue.
Copy the Refresh token and paste it into ChatBot > Settings > Artificial Intelligence > Google > Refresh token.
You are done!
If you want to activate the Dialogflow chatbot, check Settings > Artificial Intelligence > Google > Dialogflow chatbot.
Also, you have to enter your chatbot Project ID or Agent Name, to get it follow the steps below.
Note that the app does not need to be approved by Google.
If you are a Google Workspace user, go to https://admin.google.com/ and click Google Cloud Session control.
Set Re-authentication policy to Never require re-authentication.