Ok I was able to resolve, but I think it's a bug:
I swept the sand away from EDIE and then I was able to access the upgrades menu. Tutorial should probably have a step that makes the user do this, so it's discoverable.
In the upgrades menu, I went Mechanical -> Workbenches and saw that Weapon Workbench was already unlocked. Odd...
Exiting the menu, I tried to build the weapons workbench and yes, now it's unlocked.
So looks like a bit needs to be flipped somewhere so that bench is available without having to go to upgrades menu... I'm guessing you wanted to save that for later in the tutorial?
BTW, upgrades menu is AWESOME, love the design of it, sounds, etc! Great job!