Reproduction steps:
1. Open the attached “IN-78881 Canvas UI Reflection Probe Bug.zip“ project (the link is in the internal comments)
2. Open the “SampleScene”
3. Observe the Game view

Expected result: Both the “Raw Image” GameObject (right) and the “Quad” GameObject (left) have a Skybox-like reflection
Actual result: The “Raw Image” GameObject appears black

Reproducible with: 2021.3.40f1, 2022.3.38f1, 6000.0.11f1

Reproduced on: Windows 11 Pro (23H2)
Not reproduced on: No other environment tested

Notes:
- Reproducible in a new project
- Reproducible in the Player
- Not reproducible with the “3D (HDRP)” Project Template (Project Templates tested: “3D” (Built-in), “3D (URP)” and “3D (HDRP)”)
- All Graphics APIs available for Windows reproduce the issue
- The World Space Canvas UI elements do display Specular Highlights and Environment Reflections set in the Lighting window but not the reflections from Reflection Probes
- The UI element used in the reproduction project is a Raw Image but all other UI elements exhibit the same behaviour with reflections
- To be able to see the reproduced issue in a new project more clearly, make sure to set the “Source” property to “Custom” and keep the “Cubemap” property set to “None (Texture)” in the Lighting window > Environment tab > Environment Reflections. This will disable the Skybox reflection provided by the Lighting settings