Ps4 voucher card from abroad?

My cousin is in Poland and has taken his German ps4. He has a German account and so on. He bought a Psn gift card in Poland, but it did not work. We tried to change the Store region to Poland, but it still did not work. What can we do?

Nothing, they stole the coupon code in Poland. No fun, unfortunately nothing works, the map is only for Polish accounts. So Sony can make even more money. Simply set the codes Country specific and already buys the disappointed buyer again.