OneSpan Sign integrated with Salesforce Communities

We’re looking to use OneSpan Sign directly in a Salesforce Community (Community Plus licenses) out of the box but it's not working.

We're trying to do it using the method in the "Creating a Transaction from a Custom Action" section of this page: https://community.onespan.com/documentation/onespan-sign/guides/connector-guides/developer/creating-transactions-programmatically and we've given the community user access to all of the OneSpan pages, objects, fields, etc.

It looks like OneSpan assumes that an internal user is initiating the process and automatically does the redirects to the OneSpan server with the appropriate query string values to create the new transaction and redirect back to the Salesforce page.

This does not work in the Community. Have anyone integrated OneSpan into a Salesforce Community?

This is the error you see when you click on the action