DBMS_CRYPTO – ORA-06521 PL/SQL: Error mapping function

PACKAGE:

user/password — SYSTEM/SYSTEM

CREATE OR REPLACE PACKAGE enc_dec
AS
   FUNCTION encrypt (p_plainText VARCHAR2) RETURN RAW DETERMINISTIC;
   FUNCTION decrypt (p_encryptedText RAW) RETURN VARCHAR2 DETERMINISTIC;
END;
/

CREATE OR REPLACE PACKAGE BODY enc_dec
AS
     encryption_type    PLS_INTEGER := DBMS_CRYPTO.ENCRYPT_DES
                                     + DBMS_CRYPTO.CHAIN_CBC
                                     + DBMS_CRYPTO.PAD_PKCS5;
     /*
       ENCRYPT_DES is the encryption algorithem. Data Encryption Standard. Block cipher. 
       Uses key length of 56 bits.
       CHAIN_CBC Cipher Block Chaining. Plaintext is XORed with the previous ciphertext 
       block before it is encrypted.
       PAD_PKCS5 Provides padding which complies with the PKCS #5: Password-Based 
       Cryptography Standard
     */
     encryption_key     RAW (32) := UTL_RAW.cast_to_raw('MyEncryptionKey');
     -- The encryption key for DES algorithem, should be 8 bytes or more.

     FUNCTION encrypt (p_plainText VARCHAR2) RETURN RAW DETERMINISTIC
     IS
        encrypted_raw      RAW (2000);
     BEGIN
        encrypted_raw := DBMS_CRYPTO.ENCRYPT
        (
           src => UTL_RAW.CAST_TO_RAW (p_plainText),
           typ => encryption_type,
           key => encryption_key
        );
       RETURN encrypted_raw;
     END encrypt;
     FUNCTION decrypt (p_encryptedText RAW) RETURN VARCHAR2 DETERMINISTIC
     IS
        decrypted_raw      RAW (2000);
     BEGIN
        decrypted_raw := DBMS_CRYPTO.DECRYPT
        (
            src => p_encryptedText,
            typ => encryption_type,
            key => encryption_key
        );
        RETURN (UTL_RAW.CAST_TO_VARCHAR2 (decrypted_raw));
     END decrypt;
END;
/

grant execute on enc_dec to SBOL_WEB;
create public synonym enc_dec for enc_dec;

drop  public synonym enc_dec;

SCHEMA

user/pass – SBOL_WEB/123adc

CREATE TABLE users (
   userid       NUMBER,
   username     VARCHAR2(30),
   userlocation VARCHAR2(30),
   password     VARCHAR2(200),
   CONSTRAINT users_pk PRIMARY KEY (userid) 
);

insert into users
values (1,'JAMES','TEXAS','james123');

insert into users
values (2,'JONES','TEXAS','jones001');

insert into users
values (3,'ALLEN','TEXAS','allen789');

select enc_dec.encrypt('Hello World') encrypted 
from dual;

Error:

ORA-06521: PL/SQL: Error mapping function
ORA-06512: at "SYSTEM.DBMS_CRYPTO_FFI", line 3
ORA-06512: at "SYSTEM.DBMS_CRYPTO", line 13
ORA-06512: at "SYSTEM.ENC_DEC", line 21

Please help me to solve this issue.