my 2000 reg clio wont start?

i have a 2000 reg renualt clio and i wont start, it comes up with a stop light which doesn't go off and the immobiliser light stops flashing when ignition is on. but it just wont start. i dont know what else it is. ive done bypass sequences but surley i shound not have to do that. the batery is fully charged. ive disconnected me alternator as im putting new paarts on could that be part of the problem?