This is caused by a stale local workspace record on your machine, not your login itself. Make sure you have registered an account and opened a workspace at lepton.ai first, then upgrade to the latest leptonai package, list your workspaces with lep workspace list, and remove the local workspace record. After deleting the local workspace the login goes through fine. Source: https://github.com/leptonai/leptonai/issues/432
Source: https://github.com/leptonai/leptonai/issues/432