Why is the click box Failure Caption Display property disabled?

Question

Slide is 10 sec long. Click box appears at 7 sec, display to end, pause for response and failure caption, 2 attempts allowed before continuing.
Failure caption > Properties > Display time is disabled--and set to 10 sec.
Only want 3 sec with fade in and out 0.5 sec.
This in the only one of the entire collection of failure captions doing this. While I "fixed" the slide by just deleting this one and re-doing what works, I want to know why I could not access or edit the Display time.
Thanks.

Answer 1

I expected the failure caption to last 3 sec (since that was the default for all the failure captions to begin with). There are only 2 attempts allowed before proceeding  to next slide.
So, Here's what was expected. Slide opens. Text caption must be read, then an instruction given. At 7 seconds the click box becomes active. the failure caption should be 3 sec duration with fade in and out set to .5 sec each. So if the viewer clicks inaccurately, the failure caption appears for as long as 3 seconds waiting for a response. Respond incorrectly again, the failure appears again for 3 sec then the project moves on to the next slide. If the viewer doesn't click, the slide just waits without generating a failure caption.
However, I don't know how the failure caption got set to 10 sec and I usually can modify the duration. The problem is that the duration property is disabled/not available to edit/not like the rest of the captions in the entire project. How do I activate it?