QBDL error Invoices: There was an error adding, modifying or deleting invoice because it is already in use. QB error message: The transaction could not be locked. It is in use by another user.

QBDL error Invoices: There was an error adding, modifying or deleting invoice because it is already in use. QB error message: The transaction could not be locked. It is in use by another user.

The item in question was being used on another computer in the network while the sync was in progress.  Try re-syncing.