Monitor Response Time Measurement tool - issue with displaying serial monitor

[violet atlas]

Hey I am trying to build a Response Time Measurement Tool with an ALS PT19. But I dont get any output in the serial monitor (i have a program that switches to black / white every second) . Does anyone know what the issue could be?
It cant be baud rate

[left drum]

When your question is answered use !solved to mark the question as resolved.

Remember to ask specific questions, provide necessary details, and reduce your question to its simplest form. For tips on how to ask a good question use !howto ask.

[mild chasm]

on boot, the sensor pin (for all i know) could have an analog value of above 500. since this is expected to change based on the color of the monitor, without sending a signal to the monitor to change colors, there's no reason to expect it to change color. if this is the issue then setting the led pin to low in setup would solve the issue

[violet atlas]

Chatgpt solved it with doing a query
My serial monitor is spamming 0ms (when I dont measure anything), but at least it shows some values when black and white changes