Have you tried swapping the clock and data over, you might have a wiring mistake. Swapping them over will not do any harm, it is just it would not work.
The strip is running off 5V but the teensy is only putting out a 3V3 signal. Normally this would be "just" ok, I was running some LED strips like that myself today but they were a different type. Maybe you need a buffer to boost the voltage to 5V.
Have you a 5V Arduino you could try?
Sorry I forgot but are you using the Teensy's own libiary?
If you had a scope you could check that there were signals coming out of them.