The error message you are getting could be a credential issue or blocked port issue. I would suggest 2 troubleshooting steps to help resolve this error. First, validate the Credential using RDP and 2) check the WMI port 135 and port ranges 49152 - 65535 are open.
Step 1 (Validate Credential using RDP)
RDP from the MID server to the Remote Windows host to validate the Windows credential. This will validate the credential outside of ServiceNow discovery. This step only validates the credential - because RDP communicates on port 3389 to login to the Remote Windows host while ServiceNow Discovery uses a different range of ports for login and discovery communication.
Step 2 (Check WMI port 135 and port ranges 49152 - 65535 are open)
Validate the ServiceNow Discovery WMI ports between the MID Server and the Remote Windows host are open (in the Windows Firewall and/or any firewall between the MID Server and the Windows host). ServiceNow Discovery uses WMI for discovery, therefore port 135 from the MID Server to the Remote Windows host must be open for initial communication AND high ports 49152 - 65535 must be open for the remainder of the communication. Even though this is a large range of open ports, only a portion of this range are dynamically allocated.
If Steps 1 (validated credential) and 2 (validated WMI ports are open) have been completed successfully, then I suggest troubleshooting the Windows Host itself.
