I have a 15 year old Kenmore Ultra wash dishwasher. It won't start... the lock on light comes on; then blinks.

I have tried Heated dry.. normal wash (press twice). Did not work.

I then tried heated dry, normal wash (press twice), followed by cancel. Did not work.

Any suggestions... Thanks

Here is a manual: https://dl.dropboxusercontent.com/u/8010163/Kenmore_Ultrawash_Dishwasher.pdf
Get a meter so you can check out different components. Check things like the float, the filter, and the door lock and micro-switch adjustment. The lock can get out of adjustment easily.

Good luck with the testing but you are certainly reaching, or have reached, life expectancy. You can buy almost new DWS on Craigslist for $200 or less.