I have asked about my problem on wpForo but in the end i found out that my problem is in Advanced Attachments add-on.
Today i installed the version of add-on i had stored on my PC the version 1.2.7 which is before other updates and to my surprise the attachments begin to show in the forums as it was.
See the > LINK
Also i want to say shame on your developers i had to find the issue on my own, chatted with SG host support as suggested by your Support moderators that know nothing about your products, i even moved the site to other hosting and your moderators told me it's some htaccess conflict!
So my question is, do you have any idea what is wrong with the new version?
P.s. for the info i moved the site not because of this issue!