[piper6909]

If it wasn't "good" before you added the can, and was working that night, but not the following morning, then I'm leaning towards a leak. I'm assuming you filled it with one of those hoses that have a little gauge, and not a manifold set, but you can confirm my theory by putting that hose back on it and checking the gauge.

Even if there's a leak, there will most likely still be pressure in the system even if not enough to kick on the compressor, so the fact that you heard a hiss when you were loosening the condenser doesn't mean there isn't a leak in the system.