Errno: 1452 Constraint - mysql

Question

When I try to source these tables into MySQL, and it created all the tables. Then I start to populate the tables, and it will not let me populate the last table Rental_Invoice. Any suggestions?
The error is
ERROR 1452 (23000): Cannot add or update a child row: a foreign key
constraint fails (SFRC_HIDDEN.Rental_Invoice, CONSTRAINT
Rental_Invoice_fk_Client_Contact FOREIGN KEY (Client_ID)
REFERENCES Client_Contact (Client_ID))
create table Client_Contact
(
Client_ID int Primary Key Auto_Increment,
Client_First_Name varchar(50) Not Null,
Client_Last_Name varchar(50) Not Null,
Client_Address varchar(50),
Client_City varchar(50) Not Null,
Client_State Char(2) Not Null,
Client_Zip_Code varchar(20) Not Null,
Client_Phone varchar(20),
Client_Email varchar(30)
);
create table Owner_Contact
( Owner_ID int Primary Key,
Owner_First_Name varchar(50) Not Null,
Owner_Last_Name varchar(50) Not Null,
Owner_Address varchar(50),
Owner_City varchar(50) Not Null,
Owner_State varchar(2) Not Null,
Owner_Zip_Code varchar(20) Not Null,
Owner_Phone varchar(20),
Owner_Email varchar(30)
);
create table Property_Info
(Property_ID varchar(20) Primary Key,
Owner_ID int Not Null,
Property_Type varchar(30) Not Null,
Pets set('Yes','No') Not Null,
Internet set('yes','No') Not Null,
constraint Property_Info_fk_Owner_Contact
foreign key (Owner_ID)
references Owner_Contact (Owner_ID));
create table Rental_Invoice
( Invoice_ID int Primary Key,
Property_ID varchar(10) Not Null,
Client_ID int Not Null,
Arrival_Date date Not Null,
Departure_Date date Not Null,
Deposit_Amount decimal(5,2) Not Null,
Pet_Deposit_Amount decimal(7,2),
Pet_Type enum('cat', 'dog', ''),
Cleaning_Fee decimal(5,2) Not Null,
Rental_Rate decimal(5,2) Not Null,
Method_Of_Payment varchar(20) Not Null,
constraint Rental_Invoice_fk_Client_Contact foreign key (Client_ID) references Client_Contact (Client_ID)
);

Answer 1

Initial problem
Just a random guess since I don't have MySQL installed anywhere at the moment. But Client_ID in the dependent table is a VARCHAR and it refers to an INTEGER column in the parent table.
After Edit
The foreign key constraint is caused by inserting a row into Rental_Invoice that does not have a corresponding row in Client_Contact. In other words, your data violates the Rental_Invoice_fk_Client_Contact foreign key constraint that requires that Rental_Invoice.Client_ID refers to an existing row in Client_Contact with a matching Client_ID.