I’m having a very similar problem to this question. Edit: Actually the error now says ‘invalid client configuration’ last night it was saying invalid client_id.
Specifically, I believe I’m hitting the sandbox environment with an application I’ve created (‘Sandbox - Adopterluv’ on my UAT applications page), but the dwolla page keeps spitting back an invalid client_id message. Is there anything that looks immediately wrong from what you can see below? I believe I have all the required parameters for initiating the dwolla oauth flow.