Why can't I give my bike gas?

It sounds like a dead battery. Even though it runnin it may need ECM voltage. Replace the battery so it will start on its own and see if this cures your problem. PS you battery may be good you need to trickle charge it slow for 24 hours and try again. Not bikes are not made to charge dead batteries just keep them charged.

If the bike has an inline fuel fulter there could be something small blocking the line

Did you use staboil or some other kind of fuel stabalizer? if you let anything that uses gas sit for a while, you need to use this stuff. gas will tarnish and make the parts in your carb stick, i.e. floats and needle valves. so it wont let gas into the carb. get some and drain the old gas out of the tank, put it in as the directions say, with fresh gas, start it and let it idle to get it in the fuel system and carb. then SLOWLY ease the throttle on. hopefully it will unstick all those parts and be fine, or it needs the carb cleaned out

If the battery thing dosent work

Sounds like blocked jets in the carb .strip the carb and give it a good clean