@yuyingzhao-9208 Firstly, apologies for the delay in responding here and any inconvenience this issue may have caused.
The error looks the scheduler service was not running so HPC Cluster Manager failed to connect to it.
Could you first check if there is any error info in the Event Viewer for Windows Logs -> Application and Application and Services Logs -> Microsoft -> HPC -> Scheduler?
Can you share the screenshot of the error message?