hey there!
really clean hackpad,
there are just some things that needs touching up
you should consider how the project will be assembled when designing the cad, in this case it's going to be really hard to assemble if the case is printed in one piece, and also will require supports and such
it is better to have 2 halves of a case, that way the pcb can have a way to easily go into the case!
once you do, export the .step of each individual part, (something like plate.step, top.step, bottom.step) and that should be good!
while you fix that i would also recommend putting the more detailed readme at the root of the github so it's more visible!
same thing with the onshape link, it is best if you also put it in the readme!

Please make a more polished ReadME.md on your GitHub. Your ReadMe should include multiple photos of your project, photos of the full assembly such as PCB+Case, and have a good description of your project. Please read the submission guidelines before you resubmit. https://blueprint.hackclub.com/about/submission-guidelines.