i dont understand what im doing wrong

thats 2 not 20

do u have a terminator on the last light in ur line? also how long is your cable run and what type of cables are you using? anything over 100 feet and you need to be using actual dmx cables not xlr mic. cables. let me know peace jingles.

A likely culprit may be the cable itself. I've had a string of lights totally stop responding because of a bad cable (one that I thought was in perfect working order too).

What's important here is to isolate the problem and work your way to it. Try each light in a stand-alone mode, and then try it direct into the controller. If that works, then try the second light with the controller. Then, try linking the two of them together with the controller.

Just work in some sort of progression to find out when/where/under what circumstances the trouble begins.