I tried nmap on the site you mentioned and it worked. Also, when I nmap my target machine (metasploitable 2) using Kali Linux it works. My Kali is also hosted on the same VirtualBox.
As suggested, I ran a nmap scan on the target with -Pn, but it didn't work. Here I have attached the result of the scan. Host discovery disabled (-Pn). All addresses will be marked 'up' and scan times may be slower. Starting Nmap 7.93 ( Nmap: the Network Mapper - Free Security Scanner ) at...
I use Zenmap on Windows 11 to detect open ports on Metasploitable2. The problem is that zenmap is not able to detect active hosts ( it does detect that there is a host, but it seems to be down to Zenmap). But, when run the Zenmap scan on the same target from Linux 6.0.0-kali3-amd64 then I am...