Security light flashing

Try the spare key, it's not recognizing the key chip. If no spare key available, disconnect either battery cable (positive or negative) for a minute, before reconnecting the cable turn ignition switch to on position and see if it will work. If not, you'll need to get a new key.

Its a push button start with key fab

Try spare fob. If no spare try disconnecting the battery cable as mentioned above

my 2004 toyata camry battery went dead when it got charged up my cd and tape player quit working radio works, but it wontswitch from radio to cd, i have a strutch cd in it, and now my security light keeps blinking, what could be the cause