My ryobi 14.4v cordless drill won't turn on. The

check that the battery terminals are standing up enough to make good contact in the units

check and clean ram and guide and or debris

How long have you left battery on charger? It will take about 3 1/2 hrs to fully charge. t is probably not a good idea to leave the battery in the charger for long periods of time though, so once it is fully charged put it back in the drill. When fully charged the green led will turn solid. This link will have more info on charger and battery.
http://powertool.manualsonline.com/manuals/mfg/ryobi/130155001.html?p=2 C

First, you should know your battery is a Ni-CD / NI-Mh or Li-ion battery. If it is a Ni-CD / NI-Mh battery, please fully discharged and fully charged it to prevent "Memory effect".

If it is a Li-ion battery, please charge it before you use it.

Please keep in mind that, please fully charge a battery when you store it. And, charge it again every two months.

If your old battery is dead, you can replace it with a new one. Ryobi Power Tool Battery

YOU CAN GO TO GOOGLE AND DOWN LOAD THE MANUEL.JUST TYPE IN INSTRUCTION MANUEL ROYOBI CORDLESS DRILL 1048-67479CS LITHIUM BATATERY CB 120L YOU SHOULD BE ABLE TO DOWNLOAD THE MANUEL

Depending on how old or more to the point how many times you have already charged the battery, it may be worn out. All rechargeable batteries do reach a point where they won't charge up anymore. If you have fully discharged the battery and tried to fully charge it up again and it won't take a charge or only lasts a few minutes on a charge it may be time to recycle it and buy a new one.

look at the cost of new batteries,sometimes for a few more dollars its better to just buy new cordless.some brands are very expensive on the replacement batteries.

The battery isn't any good. The charger is just going through it's regular steps. (I know how it is. I just bought two Ryobi 18 volt batteries for my Ryobi cordless drill, reciprocating saw, flashlight,
trim circular saw, combo set. $60 for two batteries)

Your drill probably has a bad or stripped drive gear. Does the drill operate in forward w/a battery that is not fully charged but yet good.?