2726 Referential constraint violation: cannot delete/update the Parent Key value.
At least one of the Parent Key (i.e. referenced columns) values being deleted or updated is referenced by some Foreign Key values. By definition, the Parent Key value cannot be deleted or updated if there exists a Foreign Key value which is referencing it. Note, this is typically caused by an SQL Delete or Update statement on a referenced table.
Delete the corresponding Foreign Key value from the Child table (i.e. referencing table) first and then resubmit the request.