Restoring encrypted database on another server (using Backup Encryption)
Create a brand new master key on your second instance. i.e. don't create it from backup you taken from 1st instance. Then restore certificate from the backup taken and then try. I guess you don't need master key and only certificate is required for restore purposes. Follow the below steps:  

Step1: Create Master Key

CREATE MASTER KEY
ENCRYPTION BY PASSWORD = 'MasterKey_Password';


Step2: Verify permissions on cert and pvt key  

Make sure SQL Server service account of second instance has FULL permissions on cert and pvt key that you created.

Step3: Create cert from backup

CREATE CERTIFICATE BackupEncryptTestCert
    FROM FILE = 'E:\GKKeys\SMGK_BACKUP_CERTIFICATE.cer'
     WITH PRIVATE KEY 
      ( 
        FILE = 'E:\GKKeys\SMGK_BACKUP_CERTIFICATE_PRIVATE_KEY.key' ,
        DECRYPTION BY PASSWORD = 'smGK_BackupCertificate_BACKUP_Password'
      ) 


Step4: Restore the DB