Hi Guilherme,
Please do not use any alpha or beta versions for developing your game. They are full of bugs.
Also do not import your project into multiple versions of Unity unless there is a very good reason for it. Whenever you switch versions, there is an additional chance to break your game. Without any backup, this means that you could lose your entire project.
Regarding the problem with the particle system, have you already tried to add Debug.Logs to your code to see what is going on during runtime? Since you mentioned that the particle system stopped working after a few seconds, maybe you will be able to figure the exact moment out.
What does ‘barely work’ mean? Were you able to detect a pattern?
The emitted particles must get destroyed after a couple of seconds. If they keep existing in the scene, it might be that the particle system stops working because of the ‘max particles’ value.
The particle system should also have ‘loop’ enabled. Otherwise, it stops emitting more particles. Since you don’t call Play() in your code, make sure ‘Play On Awake’ is enabled in the component to make it start automatically when setting enabled to true.
I hope this helped. 
See also:
- Forum User Guides : How to mark a topic as solved