where there is no 1Y notice?

CBP issue the 1Y notice to NVOCC filer when the Carrier's Master BL and NVOCC's House BL are match.

Here are the possible reasons why 1Y is not sent to NVOCC:

1. Carrier haven't filed the Master BL. You file the House BL before Ocean Carrier;
2. The Master BL Number is not match between NVOCC's House BL and Carrier's Master BL. In your House BL AMS, NVOCC need to provide the Master BL Number, sometimes NVOCC could file a wrong number or use a wrong Ocean Carrier SCAC code.  Note: Master BL Number incldues  Ocean Carrier's SCAC code and BL number(without SCAC).
3. The container info is mismatch between Master AMS filing and House AMS Filing. likely due to the container number is mismatch.
4. CBP issue or your AMS software issue: if you have confirmed 1~3 are correct, you can talk to your software provider and ask them to do a ABI Manifest Query to check the actual status from CBP database. 

FYI, for the Ocean Carrier SCAC, you may can refer here Ocean Carrier SCAC code List