ERROR -- omniauth: (myob) Authentication failure! invalid_credentials: OAuth2::Error, invalid_request:

[cameronbourgeois]

Reproduction steps:

1. Initialise oaith by visiting the /auth/myob URL
2. Select "Allow access" on the "Allow access to your MYOB Account?" screen.

Expected result:

It should redirect to my successful callback endpoint where I can get an access code for API access.

Actual Result:

It redirects to a failure callback. The following errors are in the logs:

application_1 | D, [2021-12-06T03:16:20.665570 #1] DEBUG -- omniauth: (myob) Callback phase initiated.
application_1 | E, [2021-12-06T03:16:21.135606 #1] ERROR -- omniauth: (myob) Authentication failure! invalid_credentials: OAuth2::Error, invalid_request:
application_1 | {"error":"invalid_request"}

I am fairly confident that "invalid_credentials" is a red herring here.

It all works fine and I get an access code if I follow the manual example in the myob-api gem. I have other oauth integrations however, so I would prefer not to manually craft this.

My config is fairly straightforward:

Rails.application.config.middleware.use OmniAuth::Builder do
    :myob,
    ENV['MYOB_API_CONSUMER_KEY'],
    ENV['MYOB_API_CONSUMER_SECRET'],
    redirect_uri: ENV['MYOB_API_AUTH_CALLBACK_URI']
  )
end

The relevant gems I am using are:

    oauth2 (1.4.7)
      faraday (>= 0.8, < 2.0)
      jwt (>= 1.0, < 3.0)
      multi_json (~> 1.3)
      multi_xml (~> 0.5)
      rack (>= 1.2, < 3)
    omniauth (2.0.4)
      hashie (>= 3.4.6)
      rack (>= 1.6.2, < 3)
      rack-protection
    omniauth-myob (0.0.2)
      omniauth-oauth2 (~> 1.1)
    omniauth-oauth2 (1.7.2)
      oauth2 (~> 1.4)
      omniauth (>= 1.9, < 3)
    omniauth-xero-oauth2 (1.0.2)
      omniauth (~> 2.0.0)
      omniauth-oauth2 (~> 1.7.1)