PL9823 data line corruption when using 3v3
Often input levels depend on supply voltage. When you are powering the PL9823 with 3.3V, you are using it outside of its spec, it says Vdd=4.5V to 6V. So it was unlikely to work already.

Use a single MOS transistor as a level shifter:







simulate this circuit &ndash; Schematic created using CircuitLab