Oracle APEX PL/SQL Procedure Debugging?

I am using a PL/SQL Procedure to Insert one Table that was previously generated into another exisiting table:
INSERT INTO REI_LABOUR_COST (DEALER_NUMBER, DEALER_STATUS, BILLING_PARTNER, BSI_GW, YEAR, QUANTITY_FRU, LABOUR_EUR, LABOUR_LOCAL, REQUESTED_RATE)
select c001 as DEALER_NUMBER
     , c002 as DEALER_STATUS
     , c003 as BILLING_PARTNER
     , c004 as BSI_GW
     , c005 as YEAR
     , c006 as QUANTITY_FRU
     , c007 as LABOUR_EUR
     , c008 as LABOUR_LOCAL
     , c009 as REQUESTED_RATE
from apex_collections col
where collection_name = 'COLLECTION' and seq_id != 1
order by seq_id;

But it does not work. There is no error message or other sign of the procedure failing, but it does not show any results in the final table.
First question, is there any sign what I did wrong?
Second question, where would I see an error message if the command fails? Can I enable it somewhere?

Before making the insert into the database, the apex collection must be updated for each member attribute.
First Apex process: On Submit and Before Computation
declare
    y pls_integer := 0;
    v_msg varchar2(4000);
begin
    if not apex_collection.collection_exists(p_collection_name=>'COLLECTION') then
wwv_flow.debug('No Apex collection found!');
    else
for x in (select * from apex_collections where collection_name = 'COLLECTION' and seq_id != 1 order by seq_id) 
loop
y := y+1;
apex_collection.update_member_attribute (p_collection_name=> 'COLLECTION', p_seq=> x.seq_id,p_attr_number =>1,p_attr_value=>wwv_flow.g_f01(y));     
apex_collection.update_member_attribute (p_collection_name=> 'COLLECTION', p_seq=> x.seq_id,p_attr_number =>2,p_attr_value=>wwv_flow.g_f02(y)); 
apex_collection.update_member_attribute (p_collection_name=> 'COLLECTION', p_seq=> x.seq_id,p_attr_number =>3,p_attr_value=>wwv_flow.g_f03(y)); 
apex_collection.update_member_attribute (p_collection_name=> 'COLLECTION', p_seq=> x.seq_id,p_attr_number =>4,p_attr_value=>wwv_flow.g_f04(y)); 
apex_collection.update_member_attribute (p_collection_name=> 'COLLECTION', p_seq=> x.seq_id,p_attr_number =>5,p_attr_value=>wwv_flow.g_f05(y)); 
apex_collection.update_member_attribute (p_collection_name=> 'COLLECTION', p_seq=> x.seq_id,p_attr_number =>6,p_attr_value=>wwv_flow.g_f06(y)); 
apex_collection.update_member_attribute (p_collection_name=> 'COLLECTION', p_seq=> x.seq_id,p_attr_number =>7,p_attr_value=>wwv_flow.g_f07(y)); 
apex_collection.update_member_attribute (p_collection_name=> 'COLLECTION', p_seq=> x.seq_id,p_attr_number =>8,p_attr_value=>wwv_flow.g_f08(y)); 
apex_collection.update_member_attribute (p_collection_name=> 'COLLECTION', p_seq=> x.seq_id,p_attr_number =>9,p_attr_value=>wwv_flow.g_f09(y)); 
end loop;   
    end if;
exception when others then
    v_msg := ''||sqlerrm;
    wwv_flow.debug('ERR: '||v_msg); 
end;

Second Apex process: After Submit
declare
    v_msg varchar2(4000);
begin
    for x in (select * from apex_collections where collection_name = 'COLLECTION' and seq_id != 1 order by seq_id) 
    loop
begin
INSERT INTO REI_LABOUR_COST (DEALER_NUMBER, DEALER_STATUS, BILLING_PARTNER, BSI_GW, YEAR, QUANTITY_FRU, LABOUR_EUR, LABOUR_LOCAL, REQUESTED_RATE) 
values(x.c001, x.c002, x.c003, x.c004, x.c005, x.c006, x.c007, x.c008, x.c009);
exception when others then
v_msg := ''||sqlerrm;
wwv_flow.debug('ERR_1: '||v_msg);
end;
    end loop;   
exception when others then
    v_msg := ''||sqlerrm;
    wwv_flow.debug('ERR_2: '||v_msg);   
end;