Mat Ah, sorry - yeah, right you don't have an Agile Charge window configured.
We'll get a fix out.
In fact, the better work around for your scenario is to configure any Agile Charge window eg. 00:00 and 01:00 and choose a number of 0 charge slots (we currently require it to be at least 1).
That way, the window will be looked at and the pricing rules you configured will be applied.
We will update the validation rule to allow this.