When rendering on my computer the model is all reflective, but when I upload the blender file to render.st to be rendered remotely it is almost as if the body of the car is receiving no light. The window panes still reflect the HDRI though, and in a seperate test I confirmed the HDRI is being included.
It would make sense to contact the render farm themselves and ask the same question unless you have already or there's no one to contact.
I have never used render street so can't help much. I normally use GarageFarm and they have support team 24/7 avialble via a live chat so I never have to worry about something not working.
It is possible that there is a problem with the car body mapping in your file, for example, it cannot be found or is missing. You need to package up all the contents of a scene and upload it to the platform to get a good render result. Also, incorrect naming of files can lead to bad rendering results.