Working on the QuickBooks software and suddenly a warning error message popped up on the screen that indicates QuickBooks error -6190 and -816. Found this relatable? Well, this is a common situation that we might come across when multiple users try opening the company file in single-user mode. Another situation when users can bump into QuickBooks error code 6190 and 816, in case of any discrepancy between the transaction file and the company file. As a result of this error, you could lose all the important files that are saved within the QBW file.