{"error":"invalid_client","error_uri":"https:\/\/login.microsoftonline.com\/error?code=7000215"}
Reason: The configured client secret in the application is incorrect. Either the value is incorrect (configured the value from different application) or users might have configured the secret id value in the client secret field.
Resolution: The text under "Value" should be configured in the client secret field. If this value isn't stored anywhere (viewable once and it will be masked after that), create a new client secret and configure it in the application.
Preferably try saving the settings in Firefox browser.