accessing my desktop in order to merge with the online version

Which QB Desktop year version did you use?

What do you mean by "merge"? Do you need to convert your data to a new blank QBO account or do you already have data in QB Online?

I've got some troubleshooting steps so you can access your QuickBooks Desktop (QBDT) company file and complete your task, @slh70. 

Before doing so, can you tell me what you mean by merging your QBDT to QuickBooks Online (QBO)? Please know these are two separate products, and data in these versions don't automatically sync. The company should work with either QBDT or QBO.

To access your QBDT company file, make sure that it is updated to its latest release. This process resolves minor bugs and program issues preventing you from opening the company file. After that, open a sample file to determine if your company file or QuickBooks is the issue. Here's how:

1. Open the Windows Start menu.
2. Press CTRL on your keyboard and select QuickBooks. Don’t let go of CTRL until QuickBooks opens.
3. Select Open a Sample file.

If you can open the file, close QuickBooks then suppress the QuickBooks application. I'll guide you on how:

1. Press and hold the Ctrl key, then double-click the QuickBooks Desktop icon.
2. Important: Don't release the Ctrl key until you see the No Company Open window, QuickBooks freezes or gives you an error.
3. Select a company file, then choose Open.

However, if you still can’t open your company file, run a repair to replace all damaged installation files. Then, start QuickBooks and open your data file. 

For more information, check out this link: Can't open your company file in QuickBooks Desktop.

Moreover, if you want to migrate your QBDT data to QuickBooks Online, you can do so by following the process outlined in this article: Move your QuickBooks Desktop file to QuickBooks Online.

Let me know in the comments below if you have further questions about opening your company file, @slh70. I'll be more than happy to provide additional help.