I had an issue with a key from the game vault showing on steam as invalid. With every other game vault key I've used the copy button, but this time it didn't work. For some reason, the copy button below the key and the text for the key itself contained a hidden character. I've never had that issue with other keys before, but if someone has a similar problem in the future, I'd recommend typing it out yourself.

I claimed a Grimstar key from the game vault and steam says it's invalid. Does anyone know how to fix it?