Maybe the power plug on mainboard got dry joints therefore battery was n ot charged anymore and without knowing you have used the unit until the battery went flat and now when you try to power up light is flashing indicating a flat battery whilethe power adapter is plugged for nothing as the power plug is dry jointed. Have to dismantle the unit, inspect the power plug and clean / resolder
This problem is common for these presario laptops. My last one was an r3360. luckily its plug was fine, but on r3000forums.com it was quite common, as the plug is soldered directly onto the board.