model not slicing wall fill issues

[airscapes]

you model has no thickness.. the walls must be multiples of the nozzle diameter. So if you have a .4mm nozzle the thinnest thing that will print correctly is a single wall that measures .4mm thick.. you would be best off to make your wall thickness at least 2x or more your nozzle diameter. I use onshape.com for my CAD software, it is free but you r models are free for anyone else to use who has an account.. It is similar to Fusion 360 from what I have read.
I will attach a box i made for an electronics project so you can see what I mean.. I printed it with a .75mm nozzle .