ARD Problem 10.9.2 Clients

I am having a problem with ARD. My server is running 10.6.8. I have ARD 3.7.2 installed on my workstation, which is running 10.7.5 in order to do so. I am unable to add or control my new lab computers running 10.9.2 and have ARD 3.7.1. I have tried to add them to a list, but they will not be verified. I also tried to control them by clicking on the scanner and finding them, but after putting in the username and password, it is not verified. I even went into a client and changed the username and passwords, but to no avail. However, I AM able to control computers that were in the lab that are now in other classrooms. Most of those computers are running ARD 3.4. I am perplexed!. Do you know what am I forgetting to do? Thanks!