The message you are seeing is due to Caspio Bridge enforcing the Unique integrity rule of a field in your table. Submitting any record that violates the Unique rule is not allowed.
For example, if your email field is set to unique, it is not possible to enter a duplicate email address.
Note that “blank” is also considered a value. As a result the unique field can only be left blank in one record.
To see or change the “Unique” property of a field, open the table in Design mode.