cant buy Zp

can someone help me

i buy a visa to buy zp aam trying to buy alot things on it and it work good

but when i try to buy zp it not work donno why but i didnt find my country in buy windows

i live in palestine terottore

and now there is a message show when i try to buy

" access denied " " ur dont access validation secure "

so if can someone help plz help me and i will be thanks