WatchMyLan cannot find devices

I know this is not really an Umbrel related issue, but I thought it may depend on some setting I missed.

I installed WatchMyLan, and it does not find any of the devices connected on my network. None.

I am no expert, but I have a basic knowledge of networks…is there something I am missing? Any port I should open?
Also, is there a way to access UmbrelOS running on RaspberryPi via SSH? I tried using macOS Terminal, but after entering IP and user with the ssh command, the password is not accepted for some reason (I checked and double checked, it does not work)

Thank you in advance