I create curve and add resample node to it and I try to birth particle to every point of curve and using “npoints()” function to limit number of particle into
Impulse Activation and Const Activation . The problem is i don't know why sometime it generate error and sometime not.. my script is
“if(npoints(”../../popnet1“)<npoints(”../../resample1),1,0)"

If you're having the popnet reference itself, then that won't work. On the Popnet node itself you can set a maximum number of particles, try that out.

Use an add sop to delete the curve geo but keep the points, then..

In the Impulse activation set it to
$F == 1

In the Impulse amount set it to
$NPT

If all you are wanting is a single particle to be sat at every point on the incoming geometry, then this is much simpler than using an if()