Hey @pepijin
It's not just you - the scheduling feature on Steemauto worked fine up until a couple of weeks ago. Suddenly it stopped working.

I started to use Steempeak for scheduling posts. I don't know if you have come across Steempeak yet? It's basically a more advanced version of SteemIt. You can use it to read your feed, publish (and save!) your posts, and normally schedule them too - but I can't get that feature to work either since a week or two.

I have just managed to schedule on through Steemauto, though. I still have to wait and see if it will actually be posted, but at least I was able to upload and schedule my post, which is more than I could do these last couple of weeks. Fingers crossed that the issue has been fixed...