Duo on IMac authentication not being prompted

Hello All

Apologies if this is a duplicate post, but we have started using Duo and on all our windows machines it runs smoothly, however on the 2 imacs we have, it wont prompt for any authentication on mac applications. Now am I being really stupid but do I have to enable protection on MacOSX in the applications list on the admin panel before it will prompt?

I did check and the applications are enabled, but when using Global Protect VPN it wont connect but there is no Duo Popup? am I doing something wrong