From Humble WB Games™ Classics Bundle.

This key is only available in the countries listed below. If the gift recipient is not located in one of these countries, they may not be able to redeem the key.

AG
AR
BB
BO
BR
BS
BZ
CL
CO
CR
DM
DO
EC
GD
GF
GQ
GT
GY
HN
IN
JM
KN
LC
MX
NI
PA
PE
PY
SR
SV
TT
UY
VC
VE