There a couple different types of reflection. We need to know which you mean.
In the visual tab, you can turn on IBL and change the image used by double clicking on it to load a different one. It has a blur option. This is what will reflect on PBR shiny materials.
You can also enable reflection in the material settings. It works in the traditional shader as expected, but if PBR, requires the opacity be set at 99 to work. This a realtime reflection, but only works well on curved surfaces. It also cannot be blurred.
So if you post your visual tab IBL settings and material tab settings, it would help us figure out what's up. Screencaps of both.