Intermatic outdoor can't reprogram. display reads NoOp
Les, First thing to do is to change the battery and see if the timer will allow you to reprogram it. Sometimes these timers will fail, as some models have a known history of failing fairly often.
NoOp, means non operating within the Intermatic line of electronic timers, so in order to see if the unit has failed or is just malfunctioning, due to a weak battery, remove the existing battery and install a fresh, new one.
You can remove the existing battery by flipping down the front switch panel and removing the battery tray with either your fingernail or a small flat bladed screwdriver. As your timer is showing the NoOp, you don't have to worry about losing your programmed on/off cycles, so you can take your time. Normally, if you're changing the battery, you get about 30 seconds to do this with some models of Intermatic timers, or you'll lose the settings. The newer models store the program regardless of how long it takes to change the battery.
Once you've replaced the battery, press the Reset button on the timer and allow it to refresh. If the NoOp is gone, just reprogram the timer with your on/off cycles and days and you're back in action. If the timer doesn't clear, you'll likely need to replace it, as it could be damaged and will not be able to be programmed again.
Usually, changing the battery and resetting the timer works about 60% of the time for me, as I've installed thousands of the various Intermatic timers in customer's homes over the years.
Hope you find this Very Helpful and best regards!