Thank you for the additional information, KLE24. It's helpful to know you successfully opened the file in QuickBooks 2009 and updated it to QB Desktop 2021. However, the error you're experiencing when trying to open the new 2021 file suggests potential issues with the conversion process or the resulting file. Let's address your concerns about running QuickBooks File Doctor and provide some additional guidance.

To answer your question, yes, QuickBooks File Doctor does require an internet connection to download and run properly, but once it's running, it should be able to continue its diagnostics without a constant internet connection.

The time it takes for File Doctor to complete its diagnostics can vary greatly depending on the file size, complexity, and the specific issues it encounters. For a 311KB file, it shouldn't typically take more than a few hours. However, if it's been running for over 26 hours, there might be an issue with the File Doctor process itself. For the smaller company files (30KB-50KB), the process should be quicker.

If File Doctor has been running for an excessive amount of time, I suggest contacting our QuickBooks Desktop support. They can provide the details and assist you in the process.

Here’s how:
 

1. Go to this link: QuickBooks Desktop support.
2. Select QuickBooks Desktop and Continue.
3. Choose which edition of QBDT you are using and provide brief description of your concern, then click Continue.
4. Pick one how do you want to connect with us.

• Chat with us- To start conversation with an expert
• Callback- We’ll save your spot in line and call you back.

Moreover, I’ve added this article for your detailed information in fixing Error 6123, 0 in QBDT: How to fix Error 6123, 0.

Remember, when dealing with financial data, it's crucial to maintain regular backups of your company file. This can save significant time and stress in situations like this. If you encounter any other issues or need further clarification on any of these points, please don't hesitate to ask. We’ll be here to lend you a hand.