An issue reported where a customer created an empty clip and pressed the User button on the Push and nothing happened, all the lights were out except for a flashing “User” light.
If this is your situation please make sure you have the latest Push firmware.
You can find more information here: https://www.ableton.com/en/articles/push-firmware-release-notes/
Also please make sure that you are using the latest Max For Live Version. Ableton does not auto-update Max For Live and this upgrade is usually the issue or the problem. We recommend that you use at least version 6.1.6 or higher. You can download the latest Max For Live version here: http://cycling74.com/downloads/