I'm getting the same onscreen error message but now seeing:
This is happening when trying to connect to my Developer company file or a prod account. My callback is https but only a dev server using ngrok for TLS. Has anyone seen this before?
HeathPR
No, this is not the same. Mine was a 504 — MYOB's backend not answering in time, confirmed by them as a fault on their side. A 403 is MYOB deliberately rejecting your request, and is an earlier step in the flow than the consent POST we were stuck on.
the redirect URI has to be HTTPS, registered in the developer dashboard, and match the request exactly. If you're on the free ngrok tier the URL changes every time you restart it, so the one registered in your dashboard may no longer be the one your app is sending.
Check they match character for character exacly. That could come back as a 403 rather than a helpful error.
If that's not it, the thing that actually got MYOB engineering to look at ours was posting the x-amz-cf-id and timestamp from the failing response headers.
