I know how important to access the program with ease, @RJ4242. Let's work together to get this fix. 

If the error occurs on multiple workstations, I recommended to check for multiple hosts and cease host activity on all workstations. This will effectively terminate multi-user access to the station. You can follow the steps below:

1. Open QuickBooks.
2. From the File menu, select Utilities.

• If Stop Hosting Multi-User Access appears on the menu, select it and then select Yes to confirm.
• If Host Multi-User Access appears on the menu, go to the next step.
  
  

        3. Close QuickBooks.

        4. Repeat the steps above on all workstations that do not host the company file.

        5. Open QuickBooks and try doing the task that caused the error. If you still get the error, go on to the next solution.

The next option that you can do is to restart QuickBooks services on the server. Here's how:

1. Go to the server and make sure all workstations have QuickBooks closed.
2. Select the Start menu and then select Run.
3. In the Open field, enter services.msc, then select OK.
4. Select QuickBooksDBXX from the Name column. The item you select depends on which version of QuickBooks Desktop you have:

• QuickBooksDB30 = QuickBooks 2020
• QuickBooksDB29 = QuickBooks 2019
• QuickBooksDB28 = QuickBooks 2018
  
  

       5. Select the Stop link. Note: This will end all users’ access to the company file.

       6. Select the Start link. This will let users access the company file again when they sign in.

       7. Open QuickBooks and try doing the task. If you still get the error, go on to the next option.

If the second solution doesn't work, you can use the QuickBooks Tool Hub on the server, which helps fix common issues.

However, if none of these steps helps to fix this error, you can do a clean install of the program to uninstall and reinstall it on your device. 

I'll attach here the full article on how to fix this for more detailed steps: Fix locked file errors in QuickBooks Desktop.

Also, you may refer to this reference if you want to learn what feature you can do in single or multi-user mode: Features available and tasks you can perform in single or multi-user mode in QuickBooks Desktop.

Please don't hesitate to reach us if you have other concerns about accessing the program or other QuickBooks-related queries. The Community is always here to provide the help you need.