I am trying to edit my SL360 slides however, each slide appears to be 'locked' and l can't work on them. Does anyone have ideas about what the issue might be or how l can 'unlock them?
Best guess: the items are locked on the Timeline. The lock column allows you to lock any or all items.
If items are locked, click the lock icon to unlock them.
Another possibility is that you're trying to edit shapes that are on the Master. But that wouldn't impact your ability to edit objects on the slide, so this seems unlikely (based on your description).
If you're still having problems, I suggest you upload a copy of the .story with one or two slides that demonstrate the problem. It's much easier to troubleshoot when someone can look at the file.