If your account storage is full and when you're trying to delete data nothing is happening, then there might still be uploads stalled in the queue which are blocking your data deletions.
Every time you modify a backed up file, save a change to your backup, or perform any other action on SpiderOak, these actions are placed in your queue in order. If there are still uploads in your queue, then these uploads will keep trying to complete before your "delete" actions can go through causing a stall.
Should this occur, you need to clear your queue. Now you will be able to delete files until you no longer exceed your space limit.
As a note, due to our No Knowledge framework we are unable to look in your account and see what is using up your space, but here are good places to start looking: