Hi,
Access your SEPM console
>Go to Clients tab
>Go to the group wherein belong the SEP client you want to reset the password
>In you Group, go to Policies tab in right pane, (together with Clients, Details and Install Packages)
>then go to General Settings
>In General Settings Tab, go to Security Settings and uncheck all the check boxes under the Client Security Settings. This will remove the password protect of the uninstallation of your client..
>click Ok to finish and save changes
>Then update your client to received the latest policies you've configured
>Then if the client successfully received the policy, you can now try to uninstall your SEP client.
Note: In your Group policies, make sure that the inheritance is disabled to configure any changes on your communication settings and policies.
Regards,
JM