You can't add or change a record because a related record is required in table <name>. (Error 3201)

You tried to perform an operation that would have violated referential integrity rules for related tables. For example, this error occurs if you try to change or insert a record in the "many" table in a one-to-many relationship, and that record doesn't have a related record in the table on the "one" side.

If you want to add or change the record, first add a record to the "one" table that contains the same value for the matching field.