Hi michal. I confirm you we do not (yet) send an email when the service is delivered, but it should be done within about 2-10 min after completing your order.
On usual reason we see is the last order step not to be completed. In most cases, we require you to enter a captcha code at the bottom left of the page to finalize "free payment".
did you go through that step ? if yes and you cant find you service navigating the "Cloud" tab at the top and then "Platform and services" section, please send me your OVH nichandle (xxx-ovh) ny private message and i will investigate it first thing in the morning.