This milestone was a real pain for various reasons, but I finally figured out a way to get it to work consistently. Once the child has the learned to crawl milestone, make sure their motives are fully in the green because you do not want them to be tired for this. Practice learn to stand two or three times in an open space. You should get a sentiment pop up from the child while doing so. Once that happens, put the child in their crib and they should pull to stand and get the milestone pretty quickly.
If you're having problems with milestones happening and only making the child glow but they don't actually get the milestone, my fix is to take a vacation in Granite Springs and rent the large cabin for a day or however long you want. Take portable crib and a tummy time mat. I was just having this problem yet again and this method works for me. Any location would probably do as I have also done in in family members house. I just find the vacation rental more convenient it is nice not having other sims there interfering.
I actually renovated the big house in granite springs and added cribs, a tummy mat, pet stuff, better beds and well, all sorts of stuff. Now it is ready and waiting for whatever I want it for and I hope this works for someone else in need. Have fun and enjoy! 🖖
