Nmap not working

for some reason nmap doesn’t work for any box I connect to. I have no problems getting on the vpn but everytime I get this message, even when scan all ports/turn off host discov. (-Pn):
" Note: Host seems down. If it is really up, but blocking our ping probes, try -Pn
Nmap done: 1 IP address (0 hosts up) scanned in 3.04 seconds "

I looked up some stuff online and changed my connection to bridged (en0 and 1) doesn’t work. any suggestions?