Can't draft

I never get the close the gap message on my iMac in Zwift, consequently I never seem to be able to draft.  I am just wondering what the key is to drafting?  I have tried everything from slowing down when coming up on other cyclists etc, but nothing seems to work.  



Are you using the Zwift TT bike in-game? If you are you get no draft from that bike.

Paul,   Thanks for the quick reply…you nailed it, I was on the Zwift TT never even noticed that.  Thanks a lot really appreciate the help!!!