Hi Tim,
Thanks for the scene-file!
A few steps
• Set the Interactive Render Region to low quality to get faster feedback.
• Set the Roughness to zero in the Material you would like to use for Reflection.
• Set the Transparency below 100% (if nothing else limits transparency, 100% will create this problem.)
Screen capture
https://www.amazon.com/clouddrive/share/SRQwMM8lPTCmMwxJ1ligOrEu6rwW1eA7GmQ15KMFkaJ
That should give you a reflection of the context.
If that is not clearly visible, switch off the Transparency for the Glass Material, just to check if there is any at all.
If the reflection is clearly visible, adjust your scene to your needs.
Let me know if that worked for you.
All the best