How to reset checkbox

Dear all,

I’d like to come back to this issue on reseting the mark on a checkbox.

In my app I have a checkbox that is used to initiate a connection to a measuring device.
Once checked, that app tries to get the connection established in the checkbox’s callback function.

However, sometimes this attempt may fail, e.g. the device is switched off. In this case I want the checkbox to become unchecked again. I tried deleting the key (if it exists) associated with the checkbox before but the box stubbornly remembers it’s previous state.

Is there some way to accomplish, what I want?

Thanks a lot!
Markus