2013 YT46KS Won't start after winter

Ok here's the story. I bought the tractor last April and it worked great all season. I put it away in my shed late fall with fuel in the tank (w/ stabilizer added) and the battery still hooked up. I went out a few weeks ago to get it set up and the battery light was red which I figured it would be. I got a Husqvarna charger that I plugged into the charging port on the tractor and connected it to a long extension cord that got plugged into the house (no power in the shed). I left it until it was fully charged but because of family/work/weather/vacation I wasn't able to try and start it until this morning. The battery light was green but it wouldn't start. I plugged it back into the charger and its been charging around an hour now. I tried to start it while it was plugged in several times but it wouldn't start and the battery light changed to yellow or red then back to green very quickly. Is it me? The battery? Something else? Help! My lawn needs to be mowed! The weeds are over a foot high!

Thanks,

Dave

Edit: the model is a YT46LS I typed this on my phone.