I know that this fix doesn't make much sense, but it worked for me and will probably work for you too. I'm kicking myself because I had this problem for an entire year, and the fix is so simple.
Make sure you have something plugged into your pedal inputs. There are two inputs next to the power button of the Push 2, and all you have to do is to make sure that something is plugged in. Doesn't even have to be connected to any pedal device, you just have to ensure that there are cables plugged into it. I hope this helps, I'm sure it will because it's helped others too. I know it doesn't make much sense, but I won't complain about something if it works. Good luck!