if you get this error in your SMF board / forums there is a really easy solution to it.
SMF The attachments upload directory is not writable. Your attachment or avatar cannot be saved.
This error shows up if you try to save an attachment like an avatar or something you try to attach to your post.
As the error already tells you, the directory for the attachment or avatar can’t be written to.
You can find the required directory with a FTP program in YOURSMFDIRECTORY/attachments/.
First make sure to CHMOD it to 777, right click on this folder in your FTP program and then set the rights to 777, you should be able to find this or else let some one else fix this for you.
Then move to the ACP (admin control panel) of SMF (simple machines forum) and switch to Forum -> Attachments and Avatars -> Attachment Settings. There you find the option to change the directory of your saved attachments (this is the folder where all the files go when you upload them for example as your avatar in the forum). Check this path and correct it if it’s wrong.
If your forum is working correctly except for the attachment issue, you can check the correct paths in Configuration -> Server settings -> Database and Paths on the settings “Forum URL”, “SMF Directory” and the other two ones.
Check if your attachment path, compared to these ones, is set up correctly.
Or correct it if you need to do so.
Then check if it works again, it should, after you’ve did these two described ways to fix this attachment issue in SMF forum software.