Hello
To resolve the issue where the Dynamic Lock checkbox is grayed out, you should navigate to Computer Configuration, then Administrative Templates, followed by Windows Components, and finally Windows Logon Options. Within this node, locate the policy titled Turn off Dynamic Lock. If this policy is set to Enabled, it explicitly disables the feature and hides the setting from users, which causes the specific message you are seeing in the Sign-in options menu. To allow your users to manage this setting, ensure this policy is set to Not Configured or Disabled. Note that if you are using Microsoft Intune or other MDM solutions, you should verify that no conflicting configuration profiles are applying a Deny setting to the Dynamic Lock CSP, as those will take precedence over local Group Policy objects.
Domic