SQL Server – Restoring Encrypted Database on Another Server

I have two SQL Server instances on same machine. I want to create an encrypted backup on one of the databases and then restore it on the second instance. I am doing the following steps:

1. Create and backup database master key in the master database which is going to be used to encrypt our certificates

   USE MASTER;
   GO
   
   CREATE MASTER KEY
   ENCRYPTION BY PASSWORD = 'MasterKey_Password';
   GO
   
   BACKUP MASTER KEY
   TO FILE = 'E:\GKKeys\MASTER_KEY.key'
   ENCRYPTION BY PASSWORD = 'MasterKey_BACKUP_Password';
   GO
   

2. Create and back up the certificate that is going to be used for encryption:

   USE MASTER;
   GO
   
   -- създаваме сертификат, който ще използвам за криптиране на backup-a
   CREATE CERTIFICATE BackupEncryptTestCert
   WITH SUBJECT = 'smGK_BackupCertificate'
   GO
   
   BACKUP CERTIFICATE BackupEncryptTestCert
   TO FILE = 'E:\GKKeys\SMGK_BACKUP_CERTIFICATE.cer'
   WITH PRIVATE KEY
   (
       FILE = 'E:\GKKeys\SMGK_BACKUP_CERTIFICATE_PRIVATE_KEY.key'
      ,ENCRYPTION BY PASSWORD = 'smGK_BackupCertificate_BACKUP_Password'
   );
   

3. Creating the backup:

   BACKUP DATABASE smGK
   TO DISK = 'E:\GKKeys\smGKFULLEncrtypted.back'
   WITH COMPRESSION, STATS = 10, ENCRYPTION (ALGORITHM = AES_256,SERVER CERTIFICATE = BackupEncryptTestCert)
   

4. Now on the second instance I want to restore the master key but I am not allowed:

   USE MASTER;
   GO
   
   RESTORE MASTER KEY
   FROM FILE = 'E:\GKKeys\MASTER_KEY.key'
   DECRYPTION BY PASSWORD = 'MasterKey_BACKUP_Password'
   ENCRYPTION BY PASSWORD = 'smGK_MasterKeyPassword';
   

   Msg 15317, Level 16, State 2, Line 4 The master key file does not
   exist or has invalid format.

Could anyone tell what is causing this?

Microsoft SQL Server 2014 - 12.0.4100.1 (X64) 
    Apr 20 2015 17:29:27 
    Copyright (c) Microsoft Corporation
    Enterprise Edition: Core-based Licensing (64-bit) on 
    Windows NT 6.3  (Build 9600: ) (Hypervisor)