Make sure your strobe electrical connection is plugged and the valve is completely closed if you're using it. I chased a slow leak one night (showed up after 2 hours) till two AM because the plug/sync cord was not installed. If you're sealed up it will stay that way. I left my Nauticam housing sealed with the green light lit up for two weeks to test the battery and finally just gave up and shut it down from boredom. I guess it's theoretically possible to just barely cross over into the green pressure region and then have outside ambient pressure, temperature or phase of the moon nudge you back into yellow. But it's easy to test, just try it again with a couple extra pumps past the green light and see if it leaks. I'm betting you have a leak as the guys have said.