Problem with uploading my mesh to s4studio

Hi. Your mesh exceeds s4s polycount limit. The most complex maxis meshes almost never go past 10K tris, yours is 46 times higher than this.
If you have a version of this hair before curves were converted to mesh, go back to it and dramatically reduce Resolution of curves
If no, select each meshgroup, in edit mode select everything and unsubdivide. Then you need to further delete edge loops. You can use decimate modifier just this time but never again for LOD 0, it is very destructive

Other issues:
- weights, uv_1 and vertex paint should be transferred from a reference of similar shape, manually making them does not produce accurate results;
- s4s uses one digit cut numbers now