I have a late 2015 iMac 27" my

I have a late 2015 iMac 27" my OS is updated, i’ve downloaded the mudfish app however when i go to open it nothing happens

ok the older version worked
  

Are you connecting VPN session through WiFi? or your mobile network?

I’m not sure you tried to change the connection protocol found under Setting menu of mudfish app.

Please try to change your connection protocol