Hello, welcome to the Samsung Community and thank you for your feedback. I understand your concerns with your device not powering on after charging for two hours and I will be more than happy to assist.
First, lets verify that your device, charger and cable doesn't have any damage to it. If they do, it could be preventing proper charging.
Check your USB connections for corrosion and bent pins
Check your device for liquid damage
Check to ensure that your cable is secured firmly in the charging port
You can perform a soft reboot like Katninja stated by holding down the power key and the volume down key simultaneously until your device restarts. This can take up to 60 seconds. If the device enters Maintenance Boot Mode instead of restarting, use the volume up or down keys to highlight Normal Boot and select it by pressing the side key.
Try using the charging cable that came with your device along with an appropriate charger. It can take up to 10 minutes for the charging indicator to appear on the screen if the battery is completely drained.
Disconnect the charger and try powering on the device by pressing and holding the power key for 15-20 seconds.
