I have experienced this problem over the past several days where WS2812 strips will not run unless I take the microcontroller ground pin and lightly touch it to its connection. Extremely lightly.
This has happened with probable 5 different strips, 3 different microcontrollers, different level shifter boards, different sets of jumper wires, different power supplies, different breadboards... on and on. If I push the ground pin fully into it's connection point the strip does not display.
Does anyone know the cause of this and how to fix it??