Hi Cowbait,
Friend, is very simple:
Before starting, backup your content.
1- In Drive (check, which is the letter of your card), is automatic.
2- In Size, is automatic.
3- In Volumen Label, is to your liking.
4- In Option, Format Type: Quick.
Format Size Adjustment: On.
5- Format (exFAT), is automatic, because it is SDXC.
6- Click in Format button (below), and ready.
Enjoy!
And then you tell us, what happened, please.
Regards, Alfred. (Google translated)