Dell venue 8 pro won’t turn on even after 2 hour of charge

I found my old Dell Venue 8 Pro model T01D in my drawers and I am trying to look at old stuff I had on it again. It of course was discharged so then I plugged in my tablet with micro-USB cable and waited 2 hours for it to charge. On Dells support website it said that it takes about 4 hours to fully charge the tablet. However, it still shows me amber light and LED flashing after 2 hours. I know that the tablet takes some time to charge for an amount enough to turn on the tablet, but that only should take ~40min. Please help, thank you in advance