UIM server hub spooler not working throwing error Could not load plugin lib

Products

• DX Unified Infrastructure Management (Nimsoft / UIM)
• CA Unified Infrastructure Management On-Premise (Nimsoft / UIM)
• CA Unified Infrastructure Management SaaS (Nimsoft / UIM)

Issue/Introduction

Production down issue.
UIM primary hub server spooler stopped working. Spooler not generating PID. UIM not processing any alerts.

Sep 15 12:51:56:241 [5632] 4 spooler: (load_plugins_from_cfg) Read plugin (pluginName=plugin_metric, pluginPath=plugins/plugin_metric/plugin_metric.dll, active=1) from cfg.
Sep 15 12:51:56:242 [5632] 0 spooler: (load_bus_plugin) Could not load plugin lib ((NO NIM ROOT)/plugins/plugin_metric/plugin_metric.dll). Reason (The specified module could not be found.)
Sep 15 12:51:56:242 [5632] 1 spooler: (load_plugins_from_cfg) Could not load plugin lib ((NO NIM ROOT)/plugins/plugin_metric/plugin_metric.dll). RC=(1)
Sep 15 12:51:56:242 [5632] 1 spooler: Not all plugins were loaded successfully

Environment

• UIM: 20.3.3
• Spooler: 9.36

Resolution

Rebooted Primary hub.