Why is credentials selection not working in VSphere configuration?

After upgrading VSphere Cloud plugin plugin, credentials dropdown is not working in the plugin configuration section.

This is a known issue, which was first reported for VSphere Cloud plugin 2.21 in JENKINS-61131.

The recommended solution for this is to upgrde to version 2.23 or higher of the plugin as this version contains the fix for the issue. You can check the plugin changelog for additional details.