problem with immobiliser? peugeot elyseo 100cc moped will not start?

hii i have recently bought a peugeot elyseo 100cc moped. when i bought it, it was running fine however the dealer said that the battery was low. when i got it home i took the battery out and charged it over night. when i put it back in a red light started flashing next to the speedo, when i turn the ignition on the red light stays on constantly and the bike wont start at all
dealer also said the ped has a brand new cdi and supplied me with 3 keys two for the ignition and a red one for a treelock
could someone please help as i no nothing about mechanics