Rub your mouse over her stomach until you hear a burp. (About 5 seconds)
For me, this has been an issue on every episode. I did not realize it takes 5 seconds, as I think after 4 seconds of no feedback that something is working, I'd just try moving my mouse differently. After trying again with this knowledge, my issue seems to be either the countdown resets whenever your mouse leaves the hitbox, or the hitbox is much smaller than expected.
Video: https://drive.google.com/file/d/1nrwzIsz-tbVPVWI3StoxQL5FAXjiHZGi/view?usp=shari...
I'm sorry it has taken me so long to respond to this. I checked the code and yes the timer resets when you take your hand off the area of her stomach. Not sure why I included that. It's common to do that in other games I've made so I probably just copy and pasted the code and didn't think to take that part out. I will fix it for future releases.