Insert into table via form field values from PL/SQL brings error.

How do I add data from a form to a table via PL/SQL?

When I click the button that calls the PL/SQL code I've written, it errors and gives me the message:  Ajax call returned server error: ORA-20876: Stop APEX Engine For Execute PL/SQL Code

Here's the PL/SQL I'm using:

DECLARE v_count NUMBER(10); 
BEGIN SELECT COUNT(*) INTO v_count 
FROM TBL_REF_LIST_1 
where LIST_CODE = :P7_LIST_CODE 
OR LIST_DESC = :P7_LIST_DESC 
OR LIST_CATEGORY = :P7_LIST_CATEGORY;  

IF v_count > 0 THEN 
:P7_RESPONSE_VALUE := 'List Item exists with one or more of the listed criteria';