If you're referring to squad war rewards, the event that happens twice a week in which you fight opposing squads, you can tap here for more info.
Your weekly PVP event reward is calculated based on the amount of blue skulls collected during over that week. Once the event ends and the rewards are made available, your account will collect it automatically the next time you log into the game (via a popup).
As the reward is received automatically when you log in, any issues communicating with our game servers (such as problems connecting to the internet) while opening the app can cause it to not be delivered. To prevent this, always ensure a strong and stable internet connection when opening Sniper 3D and attempting to collect any rewards.
There may also be a delay of up to 10 minutes once the event ends, since the system is processing and sending the rewards to all of the participating players.
If you end up unable to collect your weekly PvP rewards due to missing the collection window, or due to connection problems, there is no need to worry. Prizes are stored indefinitely in our system, and will automatically be available to you again once the following weekly PvP event ends. This means that when you collect your prizes the next week, the previous week's prizes will be delivered together with it.
If this is a common occurance, please check this article for some tips on how to improve your internet connection quality.