Alarm comes on when starting

Got an O2 TD5, In the course of checking the float switch in the coolant header tank I left the ignition on for some time. On turning on the ignition various warning lights descent, ride level ABS, red alarm etc came on. I locked & unlocked the car several times to clear the locking warning light; it changed from flickering to flashing & when i tried to start the car the alarm sounded & the car would not start. Advice please.

What's O2 Td5 and what float switch? ... as about the issue, first of all make sure there is enough battery power, eventually charge it well disconnected before you do anything else