Hey Carson, Thanks for the theme this is cool 
I can repro this. However the buttons are there only not visible.
It seems the theme button modifications is restricted to the .discourse-no-touch class which only works on non-touchscreen devices.
On touchscreen devices only the .btn custom style active which change the button background to var(--secondary) so the button color and background is same on .btn-primary as the page background and the default .btn-primary button has no border so it won’t be visible. This is happening with all .btn-primary button.
The other button types are same but the default color is different and the icon also visible so those buttons visible.