How to do any kind of data simulation in the IQ Simulator

I'm building an app that accesses multiple sensors, and I can't figure out for the life of me how to simulate data. It seems like a lot of the docs refer to an older simulator version where the workflow was different? 

I'm using the newest SDK version -- v8.1.0, and I'm trying to simulate HR and acceleration. I've tried loading in a .FIT file into Simulation -> Activity Data -> FIT/GPX Playable File, and nothing updates on my watch face even though I've written python tests for my code to ensure the sensors do work. I've also tried the Data Simulation tab and the Workout FIT File tab with no avail. 

I feel crazy, am I missing a required step or basic setting? How can I do basic interaction and simulation in the newest version of the simulator?!