The reasons why the game cannot be purchased are as follows:

1. Bank cards or credit cards are not supported: To purchase games in Hong Kong, you need to use a Hong Kong bank card or credit card. If you are using a mainland bank card or credit card, you may not be able to purchase games in the Hong Kong server.

2. Network problems: Sometimes, network problems may also cause purchase failure. You can try switching networks or logging in again.

3. Insufficient game inventory: If the game inventory is insufficient, the purchase will also fail. You can try purchasing other games or wait for the inventory to be updated.