This dialog is opened when AccdbMerge can not connect to Database Engine to process data:
AccdbMerge tries to use a Database Engine installed to your system. If it fails to do this it shows this dialog and switches to using the database engine from Microsoft Access. If running a proper 32/64-bit AccdbMerge version does not help, please check Why I might need AccessDatabaseEngine? page on product web site with explanation why it may need to be installed separately.
