Hello,

Have you created a font before load it?
If you haven't, then you can find that command at Tools->Create Fonts

In another way, you can also use createFont() for built-in fonts
Below is simple example.

I wish it might be helpful
Sou


PFont font;

void setup() {
   size(200, 200);
   background(color(0, 0, 0));
   
   font = createFont("Arial", 40);
   textFont(font, 40);
}

void draw() {
   text("C", width/2, height/2);
}