There's not a lot expert can do when a timer is not functioning because we can't see it or mess with the thing. If you lived next door, I'd be glad to try the following things:
You have the timer and the manual, and can look and see if plastic is covering battery terminals, and see if there is grease or impediment on terminals, or if battery is inserted correct direction and brass contacts touch battery, and check that battery is good, and read manual to see if there is on-off switch.
This timer works on battery, not on electric power. So if display doesn't show with battery installation, the timer simply will not work.
Some of these timers have a solar collector, and I don't know how that factors into the battery operation. It could be battery and solar have a selector switch for either-or.
Open following link for some Gardena resources, including manual and link to gardena site.
The manual might have instructions for on-off switch, or some hint.
Gardena certainly has a glossy site, but I have been unsuccessful trying to contact the company.
Their products come with warranty.
http://waterheatertimer.org/How-to-program-Gardena-C1060.htmlAdd a comment for more free help
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