Cisco port adapter not enabled

There’s a fast ethernet port adapter in a cisco 7206 router that does not have the “enable” lite on. The port adapter is “locked” in the slot. When I try to go to the interface configuration, I get an “invalid input at marker”. It’s listed when I do “show diagnostics” as “unknown port adapter”, but is not in the “show interfaces” or “show running”. Any clues on how to enable this port adapter?