Is this SP 5.1.4?
If so – can you also try to go to the forum admin > toolbox > housekeeping and click on the reset auths tool?
OK – I realise this might not sound relevant but perhaps you could check it for me anyway.
In the forum admin > components > file uploads > Settings box is the option ‘Show uploads inserted into post content (applies to images and media) in the attachments section below post content’ turned on?
Yes – I think I was chasing a bit of a red herring on that one.
In theory this should come down to permissions and only to permissions. I think you are going to need to engage the help of a user who does not see the attachment box if that is possible.
What you need them to do – and it has to be a user who does NOT see the box – is to go to their profile – select the ‘permissions’ tab and then select a forum where you KNOW there is an attachment they are unable to see.
In particular I think we are interested in the permission ‘Can download other file type attachments’ in the ‘viewing’ section. I.e., is it turned on or off.
Is that going to be possible?