Filed w/TurboTax. 6/14/21 received CP21B showing refund of $1224 (1040SR for 2020). Today is 8/4/21 received no refund. Can't contact IRS/SSA. Who should I call?

A CP 21B means the IRS adjusted your refund.  The IRS is very backlogged and all tax refunds are taking a long time.

 

Calling the IRS is a waste of time since 20 million others are trying to call because of the delays  and only about 2% of calls get answered.

 

 

Se this IRS article:

https://www.irs.gov/individuals/understanding-your-cp21b-notice

Even if you could get thru to the IRS they would read the same information that you can see in your account at the IRS ...  https://www.irs.gov/payments/view-your-tax-account