I'm creating a custom connector in PowerApps. I don't have a swagger file because i'm creating the power app from "Create from blank Template", I'm not having issues with the rest end point but rather the security section.
I'm sure I have discovered the problem. The generic Oauth2 idenitity provider that i'm using isn't implementing the OAuth2 protocol correctly. In the authorization request they require the client_secret which is wrong, and the reason i'm getting the error I was getting. I'll have to contact the identity provider to resolve this.