When opening a codesandbox from some examples', like https://reactflow.dev/examples/grouping/sub-flows, the endpoint https://codesandbox.io/api/v1/sandboxes/define fails with {"error":"Anonymous users are not allowed to create devboxes."}, when the user is not logged into CodeSandbox
This was also reported by @bcakmakoglu when logged in.
Ideally, when clicking on the CodeSandbox button in the code viewer, it should open a read-only version of the sandbox that an user can fork if logged in.