Render movie settings 4K, no Particles

Hello guys!

I am trying to make a 4K render of what i am doing right now in UE4, but with the 4K render in 60 FPS, my VFX are not present in the video .
I try to put a 4k with 14FPS and they are here. Same with for example a 1080 with 60 FPS, i have no VFX but in 1080 with 30FPS, they are here.

I clearly don’t understand why.

Did somone have a solution/explication about this?

Thx a lot!

What’s your hardware that Unreal Engine is running on?

Graphics card
Motherboard
Processor
Monitor
RAM