At the end of the Blitz event, you will need to fulfill minimum point requirement to receive the end of Blitz Ranking Reward.
To review the minimum points required, tap on the "Rewards" button for the current or on-going Blitz. After the Blitz ends, you can review your previous rank and rewards.
Please allow 24 hours after the end of the Blitz event to receive your ranking rewards from your inbox.