Explanation
The most likely causes of the issue where the new asynchronous workflow fails to create 50 VMs at once in the public cloud are insufficient storage and expired API token. Insufficient storage means that there is not enough disk space available in the public cloud to accommodate all the VMs that are being created simultaneously. This could result in errors or failures during the provisioning process. Expired API token means that the authentication credential that is used by the workflow to communicate with the public cloud service has expired or become invalid. This could result in errors or failures during the API calls or requests.
Reference: CompTIA Cloud+ Certification Exam Objectives, Domain 4.0 Troubleshooting, Objective 4.5 Given a scenario, troubleshoot automation/orchestration issues.