I'm having trouble rendering this scene I've made from Grant Abbitt's steampunk goggles tutorial. The thing is when I'm looking through the Viewport I can clearly see reflections from the material, but then when I go to render, the reflections look flat or barely visible.
Your scene environment is not set up properly. The HDRI is using an ordinary Image Texture node, not an Environment Texture node:
Deleting it and replacing it with an Environment Texture node fixes the render:
The reason the result looks okay in the 3D viewport is because it looks like you had Scene World unchecked in the scene options:
If you check that box, then the 3D viewport matches the rendered result.