Hello everyone! It's a pleasure to be here.
I'll describe my current issue with you and if anyone can offer me some help it will be much appreciated.
What I want to achieve: I want an issue that has been transitioned to status "closed" to be able to move to status "open" with the transition "reopen" for the following 7days after arrives to the status "closed".
What I did at moment:
1. All statuses can go to closed as per image 
2. I did set up a postfunction when an issue enters closed status to a custome field
So the custom field get the current date when the issue enter the status.

3. I added a post function from closed to nuevo transition that only allows the transition to work for 7d

At this point, the transitión button is not even appearing on the issue test, which is really strange. I'm doing wrong the condition that allows to transition? I think it's correct.
Or maybe I missed some step in the middle?
Any help would be much appreciated.
As an extra step, it's possible to make the button dissapear after 7days have passed in the view issue screen?
Kind regards.