Looks like it only looks up from left to right.
So the data definition was Country Name/ISO code. I copied it and changed it to ISO code/Country Name and it worked.
BUT
When I tried to autopopulate the rest of the rows, it incremented ALL the row references, including the ones in the reference range!
So I wanted this:
=VLOOKUP(C5, G5:H255, 2)
=VLOOKUP(C6, G5:H255, 2)
=VLOOKUP(C7, G5:H255, 2)
and I got this:
=VLOOKUP(C5, G5:H255, 2)
=VLOOKUP(C6, G6:H256, 2)
=VLOOKUP(C7, G7:H257, 2)
Honestly. FFS.