Yeah as TobyTheKenobi mentioned, PCK file is either missing or there's an included filetype mismatch in the export (an issue I've run into myself if you say *.* for files to encrypt, rather than just leaving that spot blank).
Viewing post in Death's lil opportunity jam comments
Yay finally got to play it! Not too bad for a first effort. Attack/Dash isn't working, but I still got the sense of what's going on in the loop between life/death. Game feel is floaty but not terrible, and that at least gave me some advantage of jumping over the zombies once in a while. Pretty okay overall and excellent choice with Godot!
I mean... just that C and X don't do anything. And I know my keys aren't broken: (cxcxcxcxcxcxcxcxcxcx yup 🤷♂️).
As for the floaty feel, play around with the gravity constant. Godot defaults to a real-life value of 9.8, but that tends to not be very satisfying in video games, particularly in 2D games. Generally I recommend at least doubling that (say 19 or 20) and then compensate with increased jump velocity to get a smooth and fast result. You can then play around with some variables and functions to make the player float for under a second at the height of the jump, or add coyote time so they don't immediately fall when walking off a ledge.