"But I keep getting calls from clients receiving Social Security, who qualify for EIPs and have not received them."

Here's my understanding, as an example: two people, married filing jointly, both get SS direct deposit to the same bank. Their info is used from SS and tax return to determine it is one Direct Deposit of $2,400. Not two individual payments as DD or check.

Yesterday, I was able to tell my mother her check is scheduled May 22.

Instead of asking on the internet, I recommend using the provided resources. It's too late to update your direct deposit info for the Nonfiler portal.

The Get My Payment portal also is a Confirm My Payment resource. It works great, every time I use it. The address info words need to be all CAPS. 

https://www.irs.gov/coronavirus/get-my-payment