Since you have to get a new battery start with that.
Install on bike and hook up to charger overnight to make sure it is fully topped off.
Then try starting the bike, even though you hooked it up to the car battery you might be using bad jumper cables or just dont have a good enough connections for the amperage draw of the starters need top be supplied.
Save yourself a lot of effort, start with a new battery installed in the bike then trouble shoot.
On these bike batt issues can drive you crazy.
I am going to assume you have already done all the obvious stuff regarding the gas and such if not....