Message Oracle ORA-39120 - Table string cant be truncated, data will be skipped. Failing error is: string

ERRORTable string cant be truncated, data will be skipped. Failing error is: string
CAUSETable data was about to be loaded into a table that already existed and the table_exists_action parameter is truncate, but the table could not be truncated.
ACTIONDetermine actual cause by looking at base error.