I have been attempting to login to Merchant Services inside QB Desktop, keep getting Error Occurred - Unable to load the page. Please try again later.

Hey there, @DA1949. 

Thanks for reaching out to the QuickBooks Community. 

Are you currently signed in as the Admin user? If not, you'll need to be signed in as the Admin to clear the error message. 

However, if you are signed in as the Admin user, let's try some basic troubleshooting steps. Such as the Quick Fix my Program tool that's within the QuickBooks Tool Hub. 

I've included some steps to use the tool below. 

First, you'll need to install the QuickBooks Tool Hub. Here's how:

1. Close QuickBooks.
2. Download the most recent version (1.6.0.3) of the QuickBooks Tool Hub. Save the file somewhere you can easily find it (like your Downloads folder or your Windows desktop). Note: If you've installed Tool Hub before, you can find out which version you have. Select the Home tab. The version will be on the bottom.
3. Open the file you downloaded (QuickBooksToolHub.exe).
4. Follow the on-screen steps to install and agree to the terms and conditions.
5. When the installation finishes, double-click the icon on your Windows desktop to open the tool hub.

To use the Quick Fix my Program tool: 

1. In the QuickBooks Tool Hub, select Program Problems.
2. Select Quick Fix my Program.
3. Start QuickBooks Desktop and open your data file.

That should do it. For additional information about this process, check out Repair your QuickBooks. 

Please let me know if you have any questions or concerns. Have a good one!