Explanation
The most likely cause of one machine being unable to handle requests after deploying a new three-host cluster with identical resource allocations is that it has an overwhelmed vCPU (virtual CPU). An overwhelmed vCPU means that there is more demand for CPU resources than what is available on the host or VM. This could result in poor performance, high latency, or errors for the applications or processes that run on that machine.
The systems administrator should monitor the CPU utilization and load on each machine and adjust them accordingly to balance the workload. Reference: [CompTIA Cloud+ Certification Exam Objectives], Domain
4.0 Troubleshooting, Objective 4.3 Given a scenario, troubleshoot capacity issues within a cloud environment.