On the Scroll Campaign: Tranchess quest, I can't mint the cube. I just get the error "You have already submitted a cube mint, please wait for completion." I don't have any pending transactions.

I'm a software engineer in Northern California. My main strengths are C++ and Python.

this usally will resovle you you do a hard browser refresh and connect discount your wallet. Congestion (as mentioned) may be a factor

Scroll has been very congested today, could always try raising your gas. 

I had to do that on a few transactions earlier today.