Did you create an ‘IP’ or a ‘port’ device?
If ‘IP’, then it seems you entered a non-matching IP address, or the PC is in standby maybe.
I think a ‘port’ device should work, as long as a PC port is open.
You can check for open ports using Fing network scanner f.i.
Example of open port search (performed on the IP address of my Homey, just as example)
