We want to follow up with this to tell you that we identified the issue that was preventing you from using certain regions from the Launchpad and we are currently working on the fix.
The root cause of the problem is the region capacity, in terms of launchable machines, that individual accounts have access to. This means that your account would not be able to launch a machine in the affected regions independently of the Launchpad. The Launchpad is just failing at recognizing this scenario for your account.
The solution would be to use a region with available capacity.