QuickBooks Error 6129 occurs when the database connection verification fails, or QuickBooks was looking to access the Company files. The error occurs due to Corrupted/Damaged (.ND) Network data file, the mismatch between the Client domain and Server and more. There are various solutions to fix QuickBooks error code 6129, some of them are listed below: 1. Rename ‘. ND File’ 2. Copy Company file to another location 3. Restart computer in the Safe Mode 4. Ensure ‘All computers’ in the same domain Get in touch with our experts if you are unable to fix QuickBooks error code 6129 0. Call us on our QuickBooks ProAdvisor Number 1-877-263-2742 for instant assistance.