This is definitely either an immobilizer or ignition switch issue.
Put hour hand in the recess under the seat and feel for moisture there. You really should pull the seat out and open the immobilizer to look for signs of corrosion. Check and clean it's cable connectors with electrical contact cleaner, also.
When was the last time you replaced the ignition switch? You should have a spare on hand for times like this. They are only $20
