Quoting directly from Missing edit link?
There are many options here:
- You are not logged on and the post is 10 minutes old or less 2. There is already a pending edit on this post 3. The queue is full, only happens rarely on new SE sites with no moderators 4. You have been banned for a week cause you submitted many rejected edits
Options 2, 3 and 4 only apply if you have less than 2,000 reputation2,000 reputation.