@ADerbyshire Apparently they have closed the beta for now, even as a paying customer with all Enterprise hubs I was given this response from support when I asked to be added.
“I was able to hear back from the more urgent request that you had for the workflow actions beta - the team has alerted me that at this time, we’re pausing beta access while we focus on making improvements to ensure our systems scale effectively. We will resume adding customers within the next few weeks. Since you have requested the beta access through your product updates tool, you will be on the list when they start to open this process again.”