Welcome, @Sayochi
Are you using Processing 3.5.x? There’s a Processing 4.x pre-release, an early/alpha version, so avoid that for now. What operating system are you using (Win/Mac/Linux)?
Try to run the simplest sketch possible, like just a one-liner with a print('hello world'). Does this work okay? Does a display window even pop-up, and is there any output in the console?