Thanks for sharing on-point details about exporting your reports to Excel, @kfrem.
Yes, you're right with figuring out that you can only update a current worksheet when you don't have colors on it and the text is not centered. Currently, there isn't an option to update a current worksheet while you're still formatting in Excel.
Since all of your worksheets aren't protected, here are the possible reasons you're unable to export existing worksheet and the error you're getting:
To help fix this, you'll first need to ensure the compatibility of the program and MS Office. You can check out this article for more information: QuickBooks Desktop System Requirements.
Second, you'll need to update update QuickBooks Desktop to the latest release. This way, it will help you get the latest features within the program.
If updating the program doesn't work, please go through the third to the last solutions through this article: QuickBooks Desktop Crashes When Exporting Report to Excel Worksheet.
Stay in touch with me how it goes after performing the steps above, @kfrem.
I'll be around to help if there's anything else you need. Take care always.