Does the file name end with .dia2025 or .diag2025 (with a g)? If it's .dia2025 it's not a TurboTax file. If it's .diag2025, with the g, you can open it with the TurboTax Desktop software for 2025. On the screen that says "Continue Your 2025 Tax Return" click "Find a Tax File." In the Open dialog, in the space for the file name, start to type "diagnostic" (without the quotes). The name of the diagnostic file will come up, and you can select it and open it.
The diagnostic file is the "sanitized" version of the tax return that you sent to an agent. It's the same as the tax return that you sent, but with all of the personal information replaced by X's or other arbitrary characters.
