Redeeming a Honkai Impact 3rd - Game Pack key is really simple, just follow these steps:

1. Download and install the game (Android, iOS or PC).
2. Log into the game. 
3. Click on your nickname.
4. Choose "Account".
5. Choose "Exchange Rewards".
6. Enter your redemption code.
7.  Get rewards!

The key is not working

If you have activated the key according to the guide but the code appears not to work, please check what type of error message you receive and depending on it follow the appropriate instructions:

• My key is Duplicated / Already used
• My key is Invalid
• My key is region locked / can't be activated in my country
• My key activated a different product
• My key did not activate all of the content