I just don't seem to be hungry, I have only had my porridge so far today, I am going to have another shake in a minute, but only because I have to, I don't have an appetite for it.
If you struggle to get them in, then leaving it so late in the day is only going to make it harder.
Think of it as medication. Ketosis blunt/takes away appetite. It gives you a false sense of satiety, but you still need the stuff. You can't go on how you feel, whether you are hungry or not.
It's a bit like saying I have to take medicine every 4 hours, but I don't fancy it, I'm not hungry for it. You would have to take it anyway.
If you find that this keeps happening and you really can't face another pack, you do need to go on a higher plan where there is no element of ketosis ie 1,000 and above.
If you want to continue with SS on 4 packs a day, then I recommend starting earlier in the day, perhaps having tetras which are quicker to drink, and just drinking them regardless of how you feel because that is the plan that you have chosen to do.
Sorry if that sounds harsh, but it's really very important that you have everything you need.