WooCommerce customers unable to post in forum

This is a followup to a previous support thread (Users cannot post topics or replies despite correct settings!) because we have gotten NO HELP and our users are frustrated (as are we).

We have a couple of different forums, but one of them is public where you just need to be logged in to use it, and we need WooCommerce Customers to be able to post new topics and replies but they can't. We are using the Ultimate Member with the UM-ForumWP connector plugin. I have ensured that none of the "disable" checkboxes are selected in UM Roles, and I have also used the User Role Editor plugin to ensure that the Customer role has adequate capabilities, but they are still unable to post! 

We have 800 people that we need to grant access to, so adding them one at a time to a UM Role (which does have ForumWP access) is not an option. We need them to have access as they are, as WooCommerce Customers.

Please help!