That's weird. I would have though the same as you if the test.file worked then the path was okay.
Even though I know it is the absolute path that is needed, not a relative path. Still I would think the test link should have tested as such.
Oh well, live and learn.
At least the issue should be done with now.

Definitely need to adjust the test script so it reports properly, but here's why it reports correct, but doesn't work.

The test script runs from the admin directory, so ../user_files looks one directory back from the admin directory.

When you try to actually attach a file, it runs from the forum root directory, so it looks for ../user_files, one directory above the forum root, which obviously doesn't exist

Just to update this topic, everything that was corrected has worked flawlessly for the last week. I do have a question about the 2M limit on file attachments. Is that something that can be changed? I don't have any reason to so but you never know. Just curious.

This is set in the php.ini file by lunar.
There is a tuturial at lunar to change it.
HERE
Since 2MB is set by the php.ini.
You still have the limits imposed by UBB.
Whichever one is less will be the limit for file uploads.

Thank you sir! 2M seems to be adequate and I don't think anyone had needed to upload anything larger. At no one has reported an issue with it. Looks like a 20 M cap is max on Lunar. Jeez! that is asking for trouble.

You bet.
I had one member that had a 9mb file he wanted to upload.
So I just FTP'd to the site and added a link to it.
By the way that UBB.Wiki site at lunar has a lot of good stuff to research when you have a question with them.
A lot better than the FAQ.