I am trying to use the Apex Debugger in VS Code (after following the steps at https://github.com/forcedotcom/salesforcedx-vscode/tree/develop/packages/salesforcedx-vscode-apex-debugger#set-up-the-apex-debugger), and I get the following error: "You exceeded your licensed number of debugging sessions. Please end other sessions or purchase more."

I have tried with scratch orgs with both "edition": "Enterprise" and "edition": "Developer" in the definition file, with "DebugApex" included in the "features" and the DebugApex permission granted to my scratch org user. The parent org for my scratch orgs is an Enterprise Edition, and under Apex Debugger it says "Your child orgs aren't using any Apex Debugger licenses. You have 1 license available.". Under Apex Debugger in my scratch orgs, it says "Your org doesn't have any active Apex Debugger sessions.".

Am I missing something that would prevent me from starting an Apex Debugger session in my scratch orgs?