I try to make a portal effect with a lot of particles, but when I render they almost completly disapear, even if I increase the numbers of partciles, it seems like they doesn't exist. Have you some advices please ?
I dont have time to dive into a hip rn, but Id suggest experimenting with your pscale value, changing your lighting setup, trying a constant shader to see if that works, etc. If none of that works, I can check out your hip later
Your scene is pretty big and I couldn't check it all. But a quick look at it, made me think that it looks like an Alpha issue. Try to set the Alpha to 1 at the end of the chain and render it. See if it helps.
If that is the case then playing around with age and Alpha or Alpha ramps will get the job done.
Also just like Midasssilver suggested pscale might be the issue, again setting pscale to 1 at the end and rendering to see if the problem is gone will help. Then you can go back and adjust it to your liking.