Has something happened in the Workflow rules?  As I have noticed that they are not working as I expected them.

I contacted the Chat help function and they have advised that (on one instance) that it is because I had two workflows happening on the same trigger, and only one will work at the same time.

However I have just created to create a workflow and the scheduled actions are not available, then I tried to modify another workflow and it has deleted my scheduled actions that I had for that workflow.