Hello. I'm trying to recreate a cute tulip bantu knots hairstyle I saw online. I plan on making 3 variations of the hair, but the problem is that some of the buds are missing when I load the mesh in TSRW. It's really strange since all the parts were visible in blender and milkshape. All the diffuse maps are properly loaded in, so there are no missing texture. What can I do to fix this?

This hair has... 50k polygons?
Even if not the culprit of this specific issue, that's far beyond the range of what is suitable for the game and will likely have exploded verts in CAS. As well as entirely unnecessary.

The .blend would be useful for finding the exact issue, but if I were to throw a guess at the dartboard it would be that those parts are in a second mesh group but have been imported into a hair that only has one. The hair will either need to be combined into one object, or imported into a clone with the same amount of mesh groups. There can also only be one diffuse map- any extras need to be combined into one image.

Oh I think that may be the issue, that there's too many polygons. I combined all the parts in the mesh tool kit with frankenmesh since joining them in blender messes up the uv map. I can not sculpt at all in blender, so I used a mesh from a decor cc and duplicated it. I've tried making the flower parts a separate part in the accessories category, but a majority of them have a black texture. The game also crashes when I try selecting the accessory, so making it all one hair piece is my best option. Do you know if there are any hairs with that high of a poly count I can use?

The polycount simply cannot be that high. You will want to look into tutorials for how to reduce it in Blender, or any other meshing program, first. The hard limit is probably 40k, for a hair with backfaces, before the IDs start causing exploded geometry ingame. Most high-poly CC creators have around 20-30k polygons, but it's entirely possible to have high quality hair at 10k and under.

You can combine meshes in Blender as long as the UV maps share the same name, which you can change from the Object Data properties (green triangle button in Blender). If they're overlapping, that's something you'll have to fix manually.

Crashing is usually caused by having no bone assignments, most other issues just look broken in CAS but no bone weights will crash the game 100% of the time.
It's a lot to get familiar with, but understanding why something is broken will take you much further than redirecting from each issue. General Blender tutorials and the official documentation are great for the mesh work- you don't really have to get TS3 specific until it's in one piece and ready to be imported.

If you are happy with a one-group mesh, you can also refer to my hair tutorial if any of the steps help getting this mesh game-ready. TSRW and Milkshape are bypassed in this method though, so if you're already learning to use those feel free to just pick and choose what tips are useful to you

Good luck!

Thank you, I'll look through your tutorial

One thing on missing hair parts in TSRW... if you used Blender to duplicate and mirror parts, the normals get flipped, making them invisible in TSRW. Been this way as long as I know, and Blender hasn't bothered to fix it.

Just to check, turn on face orientation. If you have flipped normals, select those faces and flip them back.