Drone will warn when license usage is exceeded, but has no ability to suspend an account. This error message would actually come from your version control system (github, bitbucket, etc). Based on the logs you posted, my guess is that Drone receives the webhook and then makes an API call to fetch the Yaml, and the version control returns this error.
Perhaps the account associated with the repository in Drone no longer has access to the repository or version control system? If this is the case, see this thread for details on how to resolve: How to change API call user for fetching .drone.yml - #2 by brad