Hi guys, First time post. So in the last few weeks, my sp4 won't turn on when flat and plugged in. It will take at least 4 hours or more of charge to boot, but will then show at least three quarters charge. So if it goes flat, I can't use it for at least half a day( sometimes more). Works fine when it boots though. Also, even with zero use, it goes flat in a few days, so now I have to constantly keep an eye on it in case I need to use it. Charger is fine, charges other devices ok too. Tried all keyboard shortcuts to boot, holding down power button for 30 secs etc, nothing works. It will just eventually decide to come on, I try it every few hours. Any ideas? Thanks in advance!