Just in case your next attempt does not get the mainsail up all the way there is another possibility, that the halyards have got crossed over inside the mast eg if they have been recently replaced prior to sale.
But the last bit is the hard bit normally anyhow ………..you might want to wrap the halyard around a bar a few times and then you can pull harder without the rope cutting into your hands…..but make sure the sail is not caught on anything as it could tear….