I recently created a sign-up sheet and when I asked a parent to test it they reported that they could not even see the sign up sheet. I sent them a direct link and it still was not visible to them.
I was also in this same test looking to see if I could sign up a non-family parent who already agreed to assist at an event and this did not seem possible. On the right hand side of my screen I can see the list of dens. There is a toggle button or check box at the Den Name/Number and then inside an interior square I can see the list of Den Leaders each can be checked. I tried various combinations but nothing seems to be unlocking the entire Den parent population. I can only see Leaders.
How do you have your Dens setup? Do the parents have their own account in TT or do you just put the parents e-mail for the Scout? Are parents in the Den of their Scout or a separate Parents Den? Sign Up sheets will only show adult members as eligible to be added to the sign up sheet. In my Pack I see all of the parents within each den listed there along with the Den Leaders.
Sorry for the delay in replying to this. Parents have their own TT accounts. As far as I can see parents and scouts are organized in their own den structure.
For example Den 1 - Lions (3 scouts, 3 parents)
Den 1 - Parents (3 parents)
Den Leaders (all collective den leaders)
Scout Parents (all collective scout parents)