UPS does not shutdown the NT 4.0 server

Hello.

I installed a UPS on a Windows NT 4.0 SERVER and I pulled the plug to test it.

The UPS was configured to initiate the shutdown process in 1 minute.

But… although the UPS displayed a dialog box informing me about the initialization of the shutdown process, the Windows NT 4.0 server did not shutdown. I concluded that the UPS sent the signal to shutdown but the server did not get it.

The server is an old 800 Mhz PC. Any ideas what is the problem?

The Windows NT 4.0 UPS service is set to manual and stopped. Do I have to enable it on the server?

Or, is it a BIOS issue? Do I have to enable something into the BIOS?

Thank you in advance.