Can’t get any add-ons “Could not connect to repository”

Hello,

I’m a newbie here, but just recently installed Kodi 16.1 on OSX. I’m trying to install some new add-ons, but I’m just getting the error “Could not connect to repository”, then “Couldn’t connect to network server”

I’m at a loss as to what to do next, any advice gratefully received.

Thanks!