Paid tax preparers are not allowed to use TurboTax unless they use the professional software. You cannot access an account used by your accountant. If you paid for someone to prepare a tax return for you he should have provided you with a paper copy of it.
You can get a free transcript from the IRS:
Or you can pay the IRS $43 for an actual copy of your tax return which will include copies of your W-2’s
Turbotax is not licensed for use by professionals. If the CPA used the personal version of turbotax installed on their own computer, Turbotax does not have copies of your returns. You can get transcripts from the IRS. https://www.irs.gov/individuals/get-transcript
If the CPA used Turbotax Online, it might be possible to get that account reassigned to you, but you will have to fax in proof of your identity.
If the CPA used one of Intuit's professional products, you probably won't be able to get anything from the support phone number and will have to get your transcripts from the IRS.
Use the contact form to get a customer support number.
You can also try contacting the Estate Administrator for your late CPA.
Doctors and lawyers are supposed to have a plan to transfer their records to another professional in the event of their death or retirement. CPAs might have the same rules, it would depend on the licensing requirements for CPAs in your state. It's a good idea to at least ask.