If ParticleSystem alone displays particles correctly but UIParticle does not, please check the following points:

• Shader Limitation
  • Most cases can be solved by using UI/Additive or UI/Default.
• Particles are not masked
  • UIParticle is maskable.
  • Use maskable/clipable shader (such as UI/Additive or UI/Default)
  • Set Mask or RectMask2D component properly.
• Particles are too small
  • If particles are small enough, they will not appear on the screen.
  • Increase the Scale value.
  • If you don't want to change the apparent size depending on the resolution, try the Auto Scaling option.
• Particles are too many
  • No more than 65535 vertices can be displayed (for mesh combination limitations).
  • Please set Emission module and Max Particles of ParticleSystem properly.
• Particles are emitted off-screen.
  • When Position Mode = Relative, particles are emitted from the scaled position of the ParticleSystem, not from
    the screen point of the ParticleSystem.
  • Place the ParticleSystem in the proper position or try Position Mode = Absolute.
• Attaching UIParticle to the same object as ParticleSystem
  • Transform.localScale will be overridden by the Auto Scaling option.
  • It is recommended to place ParticleSystem under UIParticle.
• If Transform.localScale contains 0, rendering will be skipped.
• If you are using Shape module, please check whether the scale includes 0.
• Displayed particles are in the correct position but too large/too small
  • Adjust ParticleSystem.renderer.Min/MaxParticleSize.