.ND and .TLG are the network data and transaction log files in QuickBooks respectively that help QuickBooks connect and open the company file. Damage in any of these files can result in QuickBooks Multi-user mode not working. Thus, you need to rename these files to fix it. To do so, follow the below-given steps:
Open the QuickBooks Desktop Company File and press F2 key to open the Product Information window.
Under File Information, you will find the location of the Company File. The .TLG and .QBW.ND files are found in the same folder.
From the location right-click on the above mentioned files to rename them.
If the above steps didn’t fix the QuickBooks Multi-user mode not working issue, you can try out other methods mentioned in the linked article. If you need further assistance, you can contact our support team.