I downloaded plugins " noraid " & " Friends API "
NO players can damage anything that is built by another...
but apparently if you use " friends API " your friends can then damage your builds.. ( doesn't work )
They still get the " cannot damage another players base " etc message
Yes ( before you say it ) they did add each other as friends but it just doesn't seem to allow damage..
any ideas or did I miss something ?

That'd be a question for the plugin developer that is utilizing this plugin; Friends API does nothing by itself.