Форумы / Cotonti / Support / Forums- Cant Delete, lock topic

Are you admin?

If you are admin, you should see:
Topic options : Bump Lock Sticky Announcement Private (#) Default Public / General discussionPublic / Off-topic Ghost Delete:[x]

You need to click on the X.

Are you userID 1?
If not, maybe you don't have admin rights in that part of the forum. Check your rights.