There are some issues here...
The first major one is you say you want Google to index attachments, but in robots.txt you are specifically disallowing them from crawling the /attachments/ directory.
You have numerous references to directories/links only seen by logged in users. Search engines will never see these, unless you specifically give them login credentials which is uncommon.
Recommend putting directories in alphabetical order, this will help eliminate duplicates.
Your current robots.txt with notes...
[CODE]User-agent: PetalBot
User-agent: AspiegelBot
User-agent: AhrefsBot
User-agent: SemrushBot
User-agent: SemRush
User-agent: DotBot
User-agent: MauiBot
User-agent: MJ12bot
Disallow: /
User-agent: Amazonbot
Disallow: /threads/*/reply unnecessary, these urls only show if logged in
User-agent: *
Disallow: /whats-new/
Disallow: /whats-new/* unnecessary exact same affect as /whats-new/
Disallow: /conversations/ old reference should be /direct-messages/
Disallow: /find-threads/ unnecessary, these urls only show if logged in
Disallow: /*/create-thread unnecessary, these urls only show if logged in
Disallow: /*/post-thread unnecessary, these urls only show if logged in
Disallow: /login/
Disallow: /logout/ unnecessary, these urls only show if logged in
Disallow: /lost-password/
Disallow: /misc/
Disallow: /online/
Disallow: /profile-posts/ not sure this directory exists (likely now a subdirectory of /whats-new/ or /members/ which are already covered)
Disallow: /*/add-reply unnecessary, these urls only show if logged in
Disallow: /*/approve unnecessary, these urls only show if logged in
Disallow: /*/draft unnecessary, these urls only show if logged in
Disallow: /*/latest not positive, but I think this is all covered by /whats-new/
Disallow: /*/post unnecessary, these urls only show if logged in
Disallow: /*/reply unnecessary, these urls only show if logged in
Disallow: /*/unread unnecessary, these urls only show if logged in
Disallow: /account/
Disallow: /members/
Disallow: /attachments/ remove if you want attachments indexed
Disallow: /goto/
Disallow: /help/ if you have any custom terms, privacy policy, or help pages you may want to remove this
Disallow: /posts/
Disallow: /login/ this is a duplicate
Disallow: /search/
Allow: / unnecessary, this is already inferred
Sitemap: https://www.nnn.com/sitemap.xml[/CODE]
I would recommend you start with this and then make any additional adjustments:
[CODE]Sitemap: https://www.nnn.com/sitemap.xml
User-agent: PetalBot
User-agent: AspiegelBot
User-agent: AhrefsBot
User-agent: SemrushBot
User-agent: SemRush
User-agent: DotBot
User-agent: MauiBot
User-agent: MJ12bot
Disallow: /
User-agent: *
Disallow: /admin.php
Disallow: /account/
Disallow: /direct-messages/
Disallow: /goto/
Disallow: /help/
Disallow: /login/
Disallow: /lost-password/
Disallow: /members/
Disallow: /misc/
Disallow: /online/
Disallow: /posts/
Disallow: /register/
Disallow: /search/
Disallow: /whats-new/[/CODE]
