Actually one other thing I’ve noticed after going through a few certificates is that they all seem to be rounded to the nearest minuet. I don’t know if they are all rounded forward (or some are rounded backwards) but with my certificate I requested it at 12:50:33 UTC but the cert was valid 12:51:00 UTC so 27 seconds later.
27 seconds might not seem like a lot but presumably it could be up to 59 seconds and if the time was correct on your laptop it might have been enough that you would have got the “Certificate is not yet valid” message on your laptop.
Rounding to the nearest minute seems like an odd decision, I wonder if there is someone who can shed some light on that?