If nodes cannot be found automatically, that could suggest:
-the connection (in any direction) is blocked by firewall/antivirus software (keep in mind that Windows Firewall / Defender / Security Essentials counts as well)
-the computers are on different subnets ("search lan" option works only on the same subnet, it uses UDP broadcast)
The solution for the above would be to enter the IP manually on the list.
Networking issues are very complex, and there is so many factors (e.g. specific router settings) that it is sometimes not possible for us to help. If you are working in a company and you have an "IT guy" or some kind of network administrator, the best idea would be to call him and provide him with the information I listed above.
Just a random idea: I had a similar problem in my home network, and after long time of tries and my head very close to exploding, I found out that resetting the wireless router settings to factory defaults solve the issue immediately.
