How can I hide the secondary menu to those not logged in?

Give this a shot:

body .secondary-navigation {
    display: none;
}

body.logged-in .secondary-navigation {
    display: block;
}

Nope and I tried this that worked but not when responsive (also dropped down the menu)

#menu-top.secondary-menu.sf-menu {display:none;}
.logged-in #menu-top.secondary-menu.sf-menu {display:block;}

That's not the same thing as the code I provided ;)

the 'nope' referred to your code, mine only worked a bit :)

Can you link me to the site where mine isn't working?

http://sandgroper.net/

Can you replace your code with the code I provided?

I did, nothing happened

ok it's running your css now

I just adjusted the CSS above to be a little more specific - should work now: https://generatepress.com/forums/topic/how-can-i-hide-the-secondary-menu-to-those-not-logged-in/#post-188374

Great, thanks Tom ;)

You're welcome :)