I have created a specific private forum for guests
There is no way to create a private forum for guests. If a forum is accessible for guests then it's accessible for all. Gust usergroup represents not-loggin visitors.
only check their private topic checkbox('Can set own topic private').
Remove this please, this cannot work. I've already explained that the Private Topic checkbox doesn't work for guests, it is impossible to create a private topic for the guest. Read my previous post again and disable this permission for guest.
Never use private topics for guests. It'll never work correctly. Guests cannot be authorized by wpForo, thus they cannot see their own replies in a private topic.
I've already explained that the Private Topic checkbox doesn't work for guests, it is impossible to create a private topic for the guest. Read my previous post again and disable this permission for guest.
I checked what you mentioned. And I've confirmed that the guest's private is not a safe private. Thank you.