i was trying to install license on mac, a message pops up saying invalid machine name, how can i fix this? thank you!

It's strange, but it looks like Houdini cannot obtain the computer name.

What is specified as Computer Name in System Preferences >Sharing ?

You can also configure your computer from Applications > Utilities > Terminal with:
sudo scutil –set LocalHostName myname
and
sudo scutil –set HostName myname.local
where ‘myname’ is the name you chose for your computer.