I have been stuck for awhile now on this.  I am using data from the Tyler Data & Insights API to autofill fields in one of my forms, when a unique ID is passed to one of the fields.   Since some of this data is private, I am using their workflow for OAuth 2.0, and I have generated an access token on their website. I have not been able to make this token work with invoke URL, but I have gotten this to work by building a custom connector with Creator.  The problem with this Creator custom connectors require a token refresh URL, which is not supported by the API where I generated the access token.  After about 15 minutes, my token expires and my connector is useless.  Even if I max out the expiration time in the connector to 24hrs.  Has anyone successfully authenticated with an OAuth 2.0 access token using invoke URL?  

Tyler OAuth 2.0 documentation: