Hi, and welcome to the community forum! I’m just another GF owner like you, but I think I know what’s going wrong.
On the right hand side of your screen, there’s an exclamation mark in a triangle above the text “YOUR FIRST PRINT … Congratulations! … Some things to remember:…”
Below that message there is a button you have to click to acknowledge it. Until you click that button, it won’t start uploading your design to print. At some screen resolutions, this button can be below the bottom of the window and there’s no scrollbar to tell you that it’s there.
If you scroll down or zoom out (CTRL and MINUS), you’ll see the button and be able to move forward. You only have to do this the first time you print something with your Glowforge.