Adobe sign trial - SharePoint integration not working

I've signed up for a Adobe sign trial and am following the steps from this document to set it up with my development SharePoint tenant: Adobe Sign for SharePoint Online - Installation Guide

When I get to the point where I need to connect the SharePoint site to an Adobe sign admin account, it doesn't seem to work. After I click on 'Connect' for 'Establish SharePoint site connection', I get a popup window where I am asked for the Adobe sign admin account details. After entering those I get another window where I see a message welcoming me but it does not show that it was successful in establishing the connection. What am I missing?