Didn't get it
Category: Asian Nations
Clue: In 1991 this became the first former Communist country to reinstate the monarchy, which it still has.
I didn't get it. I didn't have enough time to work my way to Cambodia.
But at least I didn't go with the first name that came to mind - Spain. It only meets one of the criteria (two if "reinstate" and "still has" are separate), being neither Asian nor former Communist (rather decidedly not former Communist), and reinstated their monarchy earlier than 1991 (much: 1978). I'm not sure why it was what I thought of, but it was.
One of the contestants said "Lithuania", which only meets the "former Communist" part. )I'd have rather left it blank or guessed wildly than said that - it's worse than Spain!) The others said "Viet Nam" and "South Korea", both of which left me blinking.
I'd probably have said "Laos". It's not right, and at some level I'd have known that, but those 30 seconds do go by fast.