I noticed that when unzipping the .zip file, it was putting the .pdx inside of another .pdx which did not work in the simulator, but the internal .pdx would load normally.

I updated the .zip file so that when extracted it would only be a single .pdx file, not a nested one.

Hopefully this will fix the sideloading issue people are having, but I'm still waiting on my Playdate to arrive so I can't know for sure.