I seem to have the same issue as in Limit on private workspaces on free plan? . I don’t see any private workspace in my dashboard, but I’m not allowed still to create a new one.
This can happen if you’ve already created workspaces that have been resized to have more than the standard 512mb of RAM and 2gb of disk space. If you have any of these, they are using up your quota for X number of “premium workspaces” (which is private or resized to be larger).