Hello Patrick
Definition of the workflow rule looks absolutely correct. Unless you want to define a condition (e.g. specific Accounts for which you may want this workflow to be triggered), you can leave "Define Conditions" section Empty. Define an Action (in this case an Email), define a Recipient and in the end activate the workflow rule.
I tried exactly the same thing in my system and it worked fine (attached screenshot of my rule definition).
Please be aware that you may not receive the email immediately since the activation time for the scheduler would be 00:00 UTC. In case it still doesn't work for you, please log an incident and someone from SAP support could debug this for you on your tenant.
Thanks
Karan