disappearing cluster
 

I create a a cluster for the spline. After some time, it just disappear even though i can still select it through the outliner but in my viewports, they are invisible. On top of that, the cluster also cant work at all and creating new cluster still is invisible and unworkable. so what's wrong?

In terms of it disapearing make sure show > deformers is on in your view panels.
With it not working go into its attributes and check the weight / envelope is set to 1