iMac can not see wifi home connection but it finds others
After several trials, I "somehow" managed to fix the problem.

The important thing, I guess, is that you need to reboot the iMac.
What I know for sure that I have changed is:


Add a new position;
Link a new connection to the new position;
Add an additional DNS address to the list: 8.8.8.8


The source I was following is this website with troubleshooting solutions. Hope this is useful for future reference.