If you assign it an IP that is not inside your LAN the scan usually fails. Try a netmask of 255.0.0.0 for another scan.
I have an HP 1810-48G switch that I can not find on my Network. If I do an IP Scan or use the HP Discovery Tool it does not show up. However , all 30 plus users are able to access Network drives and the internet without issue. When I originally installed I assigned a Static IP.. There is no Console port on this switch and I hate to do a factory reset. Any idea what's going on? Thanks