You’re not welcome here with a Regus membership.
There is likely internal competition between different IWG brands which is damaging their customer experience.
(Update following Regus' response: I did book a co-working desk on the app. But as soon as I arrived, I was told that, despite having a full Regus membership and being allowed to book the workspace on the app, I would not be welcome back unless my membership was with The Clubhouse)