How to use online store in steam?

[nastyajw]

Sorry for broken english.

I want to buy some packs in-game store, but it always failed.

When i tried,
"connecting to steam"
"steam overlay should appear, if it does not please make sure it you have not disable it."

and few seconds later,
"payment"
"payment refused, you have not been billed."

steam overlay is enable and steam wallet have enough money, why I can't buy anything?

[HousePet]

So is the Steam Overlay for the store opening?

[nastyajw]

So is the Steam Overlay for the store opening?

No, steam overlay isn't open. Steam overlay is enable and shift-tab is working, but overlay for in-game store isn't.