Go here in your Niagara system, whether it’s in a blueprint or just in your scene and set your bounds from 1 to 100 until it stops disappearing. I usually just set it to 100.
What you can also do is this:
This sets it in the emitter itself per emitter. This is if you’re using GPU render for the emitter and with fixed bounds set. By set I mean you will probably need to have them set to:
-1000x -1000y -1000z
1000x 1000y 1000z