Glad to have you here on the Community page, @m-gladych.
It's my priority to help you today so you'll be able to open the file emailed to you.
If you mean you're trying to open or convert an accountant's copy to a regular company file, then you can follow these steps:
Please know that the ability to convert an accountant's copy to a working file or a regular company file is only possible in QuickBooks Desktop Accountant editions.
To learn more, you can check this article: Convert an accountant's copy to a regular company file.
For your future reference about this feature, you can also check this article: Use the Accountant's Copy.
Let me know if you have any other questions and if you're referring to something else. I'll be right here to help!
I've got some steps on how you can open the file that was sent to you, m-gladych.
You can follow the steps below to restore your accountant's copy in QBDT.
However, if your client sends the email through Accountant's Copy File Transfer, you'll have to download the link by opening the email from email@example.com, Once done, you can follow the same steps provided above.
Let us know if you have follow-up questions. We'll be right here.