Licensing Backup Exec 2012

Hi guys, 

I'm new here and need help to fix a big trouble here. My backup just stopped and I really don't know what to do.

First of all, sorry for my terrible English. If I'm doing something wrong, tell and I'll try to do the right.

I bought a Backup Exec 2012 and install, configure (I think i do this in the right way) and do my backup without any problems until now. Now it's saying to me that I have to buy and install a license for Backup Exec Agent for Windows. I really don't understand it. 

In my company here, I install the Backup Exec 2012 in Server A and I was doing backup of the Server B. Do I need to install it on Server B? 

Thanks for any reply or anything else. Thanks a lot,

Carefully,  

Renan.

Ps: I attach an image.