Hi Jaqueline,
Please try below solution may be it will help you.
Solution1: Locate the Java Connection for SAP Business One DI API (default path is C:\Program Files\SAP\SAP Business One DI
API\JCO\LIB). Enter this path with double back-slashes in the JCO patch of the diproxyserver.properties file (default path is C:\Program
Files\SAP\SAP Business One Integration\DIProxy).
Solution2: Reinstall DI API from the same version as SAP Business One application. The check if sboapi.jar and sbowrapper.jar files were
created in C:\Program Files\SAP\SAP Business One DI API\JCO\LIB folder.
Thanks,
Tushar