Hello there, @pamk260.
I appreciate the steps you've done to get this working. Allow me to step in for a moment and help make sure that you can download your bank transactions in QuickBooks Desktop (QBDT) for Mac.
Since it's working on the sample file, your main company file might be damaged causing this unusual behavior. To isolate this, return let's run the QuickBooks built-in diagnostic and repair tools called to rebuild and verify data utilities. These tools comb through, repair, and notify you of data damage within the file.
Here's how:
1. Go to File, then select Utilities and Rebuild Data.
2. Choose OK. Follow the prompts to save a backup.
3. Click OK when you see Rebuild has completed.
4. Now, go back to File, then Utilities and select Verify Data this time.
5. Should the Verify find an issue with your data, you will be prompted to Rebuild Now or View Errors.
For your reference, you can also check out these articles for further guidance:
Once done, try to download your bank transactions again to double-check.
That's it! Give this a try and please let me know how it goes in the comment section below. I'm always here should you have any follow-up questions or concerns. Take care and have a wonderful rest of the day.
