You might be browning out the power supply. You are powering this with what size power supply? The power port should be directly connected to the power supply on the Raspberry Pi; if you are underpowering that, you might have a brownout.
Your best solution might be to try powering the Raspberry Pi with a charger battery that supplies 2.5A. Also, can’t tell from the video, but if you are powering this with a computer USB port, you will definitely not be supplying enough power to it.
Provided you have an adequate power supply, you might also test the voltage you’re getting on that port should you have a multi-meter.
This Grove EL Driver might also have the pins reversed.
So for instance, if you connect the driver to port D3, then it’s going to use pin number 3 off of the GrovePi board. But you can also use pin number 4 on port D3, but it’s going to be the one following the 4th.
Please look into the hardware diagram I’ve provided.