CPA Verify https://cpaverify.org/ is a great resource for making sure your CPA is actually a CPA.
Just enter the last name and see if you can find them. You can then go to the state that they are licensed in and make sure it's them. Check the address. Make sure that the person you are dealing with sounds like the licensed professional.
If you can't find them then contact the state or province they are practising in.