This is most likely a chip key malfunction .
When the security light flashes then this means the Security management system can not read the key .
Now could be just that one key so try the spare key first.
If the spare also is not working you will need a diagnostic scan tool to check for security malfunction codes .
When this happens then there is no other way to reset this without the needed tools, you will need to call out a automotive locksmith that will have the needed tools to reprogram the keys ,make sure you have all keys as programming keys all must be done at the same time.
One thing you could try first is check all fuses in the cat under the dash .
Then disconnect the battery for 10 minutes .
Reconnect and then lock unlock doors with key fob ,step in and try to start.
No start call out mobile keysmith or send to dealer .
Check your insurance you may be covered for a tow truck to get to the dealer.
Need further assistance with this issue then please get back to me with the reply box below .
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Kind regards Greg