Fairplay SPC request returns nil

I'm trying to use the [AVAssetResourceLoadingRequest streamingContentKeyRequestDataForApp: contentIdentifier: options: error:]; method to get SPC key, but I get null returned to me instead of target SPC value. I am mainly linking to the provided Fairplay sample application. I am using url host encoded string as content id and .DER certificate obtained from SPC server as application data. Has anyone else experienced this problem?

NSString *hostString = [URL host];  
NSData *assetId        = [NSData dataWithBytes:[hostString cStringUsingEncoding:NSUTF8StringEncoding] length:[hostString lengthOfBytesUsingEncoding:NSUTF8StringEncoding]];  
NSData *certificate = (obtained via Key Server).  

NSError *error;  
NSData *SPC = [loadingRequest streamingContentKeyRequestDataForApp:certificate contentIdentifier:assetId options:nil error:&error]  

      

        
        
        
      

    

The SPC output is zero here. The full description of the error is as follows:

Error Domain=AVFoundationErrorDomain  
Code=-11800 "The operation could not be completed"   
UserInfo=0x170461980  
{NSUnderlyingError=0x1740548e0 "The operation couldn’t be completed. (OSStatus error -12640.)",  
NSLocalizedFailureReason=An unknown error occurred (-12640),  
NSLocalizedDescription=The operation could not be completed}