I was supposed to get 8 $50 Savings bonds, but I have only received 7 all at once through mail. When I am supposed to get the last one or should I contact someone?

Within 3 weeks after the IRS has processed your refund, you should receive your Savings bonds. 

If this time has passed and you're still waiting for your eighth Savings bond, call the Savings Bond Processing Site at 1-800-245-2804.

This information is from TurboTax FAQ: https://ttlc.intuit.com/replies/3302482