Salesforce connector oauth settings

I am setting up the salesforce connector to sync users and when going to authorize the connector I am getting the error 'OAUTH_APPROVAL_ERROR_GENERIC : An unexpected error has occured during authentication. Please try again. ’ in the salesforce app. Do you know if there is a specific flow that needs to be enabled in the salesforce connected app setup?

thanks
Nick

I was able to get this working, but now post approval, am getting an error in IDM on update of the json for the connector saying either type of refreshToken or instanceUrl is needed?