Do you have light bulbs or LEDs connected? If bulbs, what voltage are they rated for, and do you know for sure they are good? If LEDs - what resistor do you have with them? Are they connected backwards?
You can reset the decoder to default settings by setting CV30 = 2. That will reset all function control and reset the address to 03 - try that and see if it operates correctly on address 3 and if the lights work then.
If reset fails and you know the lights work otherwise, check you wiring to make sure everything is solidly connected. If that's all good then you might have a bad decoder, TCS has a good warranty, they will replace it even if you make a mistake while installing it.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.