glediator + PL9823 (WS2812B) + teensy = fail?
G'day Guy, What you're building there looks nice. Do you have a circuit diagram you can share? Regarding the code, I've never played with FastLED.h but is the serialReadBlocking how it deals with the input data? Not that it's wrong, just not what I was expecting. 

Two things to look at:


Your serial baud rate is a bit odd, 1 million neat. Is that intended? I wouldn't think so. Most common is 9600, I have run projects at 19,200 for giggles, but I doubt that you have it correct there.
I see your project you are using multi coloured LEDs with 3+1 pins which in actual fact means you have 240 LEDs (are the last 80 segments/colours all lighting?). If your PC sending the serial stream is expecting 80x single colour LEDs (80 individual LEDS) but you've got 80x tri-colour LEDs (80x3=240 LEDs) you probably aren't lighting them all up. (I only mention this point because I noticed your PC appeared to be sending only one colour, but that could have just been the moment I saw in the video). 


edit: I meant to include this link for the teensy serial baud rate info: https://www.pjrc.com/teensy/td_uart.html