A quick tip to help you debugging your projects: you can use the virtual logic analyzer to view the signals generated by your PIO machine!

Add a logic analyzer to your project by clicking on the purple "+" button and selecting "Logic analyzer (8 channels)":

Then connect pins D0 / D1 to your DATA / SYNC lines (these are Pico pins GP2 / GP3 if you use the tv-pong project template).

Start the simulation, and you should see the Logic Analyzer's green activity LEDs blink as the data is coming in, as well as the number of samples collected:

When you stop the simulation, the Logic Analyzer will download a VCD file with the recorded signals to your computer.

You can use PulseView to open the file and view the recorded signals:

For more information and detailed instructions on how to load the signal file into PulseView, check out the Logic Analyzer guide.