VBulletin posts not including signatures

Hello.
Using SNAP to post to a vBulletin forum, using %FULLTEXT% for Post Text Format and everything is great, except my forum signature doesn’t show with the posts made by SNAP.

The show signature checkboxes are ticked, and when posting normally on the forum my signature shows without me doing anything. But on the auto posts, I have to manually edit my posts to include signature. My signature includes a link back to my blog, so I’d like to get it showing if possible.

Any ideas?

I’d include links to my site and the forum, but they’re both NSFW.