Citroen Xsara Picasso car not starting

If you mean it starts with a bump start , there are many possible causes , especially with older cars . Could get battery load tested to eliminate that firstly . Also depends if the engine is turning over when it fails to start or not .Could also check / replace plugs if needed

Yes ment a bump start and no the engine doesn't turn over when it fails the battery is only a month old and was the first thing checked all lights on dash work and there's no warnings coming up after trying for some time the battery light stays on even when the key as been removed all earth and wires checked don't know what to do next

If car was o.k for a while after battery replaced , you need to now get it checked for voltage , especially if not used a lot or for short trips . There could be a fault like the alternator not recharging the battery enough or something draining the battery causing non start

Battery has been checked and that's ok