Hello,
Is this something project specific? Or global case?
The BOM as well as Reports use rpt files. In case this is project specific try to compare reports.ini file from Project_Root/Config folder.
The RPT files are located in C:\Program Files (x86)\Bentley\Plant V8i\Reports. Check that they are available.
What version of AutoPlant you are using? AutoPlant 08.11.09.140 supports Crystal Report Engine 11.5. In case RPT files were edited with higher version they will be not user by AutoPlant.
Hope this will help.
Regards,
Artiom