With the debut of the new UX there seems to be some problem with the "Manage Connections and Gateways" experience's interaction with the users component. When you I view the Connections tab, the entire "Users" column is blank. When I go into "Manage Users" for a particular connection, the users list stays stuck on "Loading" and searching for known users returns no results, even if you provide the full user email address. This is true despite a fresh browser session in Edge or testing with an InPrivate window. Interestingly this is a problem only for the Gateways management UX, it's not a problem for Workspace Access for example.
Since the implementation schedule of PowerBI version varies from region to region, can you provide detailed version information for us to do better troubleshooting? It is available in about Power BI in the upper right corner of Power BI Service.