Welcome to "black box" approach to database development! The truth is you still need to understand how underlaying database is designed.

Now to the question. The message is clearly pointing on TL5TEST1.SYS_C0022921 foreign key constraint. It is telling you that the parent table it references does not have the primary key value for the record your application is trying to insert into the child table.
The following query will give you parent table, child table and PK constraint referenced by the FK constraint above:

select b.table_name parent_table,
b.constraint_name pk_constraint,
a.table_name child_table
from user_constraints a,
user_constraints b
where a.constraint_name = 'SYS_C0022921'
and b.constraint_name = a.r_constraint_name;

You need to be logged in as the schema owner to run this query. Otherwise you should be looking for the data in all_constraints instead and add predicates for column "owner".