Thanks for contacting us regarding your recent upgrade, @RMI - MD,

If you're referring to the insufficient Multi-user permission error after upgrading the company file, there are a few reasons why this is happening. Check out the following scenarios:

• Saving the company file in a protected location such as the root of C:// Drive or Program Files of a Windows Vista, 7 or 8.
• The file is located on a restricted location.
• Folder permissions are updated or not set up properly.
• The folder where the company file is saved is damaged.

To resolve this, there are a few troubleshooting steps we recommend that you follow. See the complete solution by clicking the following link: QuickBooks Desktop Users and Restrictions

However, if you're referring to the user access to log in to the company file, it should not change after installing updates or upgrade. If these users are unable to get in, make sure they are on the correct company file. If you're using the right one and still unable to successfully sign in, perform the steps found in this article: Resolve data damage on your company file

Let me know the result as I want to ensure this is all taken care of. I'll be right here if you have questions or clarifications along the way. Have a good one!