I'd suggest some dirt may have got inside the barrel or the ECU connection is faulty.
You might consider taking the ignition barrel out and either having a go yourself or take it to a reputable locksmith. Insofar as bad ECU connection - usual terminal clean up might work.
Finally, look to scrapper 2nd hand option - but if you have the immobilising ignition/chip in the key, it could be a waste of time.
Good luck