Visual Studio 2017 doesn't see mapped drives

Question

I'm running Visual Studio 2017 on Windows 10 1803 64-bit. I have a mapped drive (H:) and when I try to run an SSIS package that depends on finding files in that drive, it tells me the files can't be found. If I change the code to use a UNC path, it works fine. However, in this case I'd really prefer using the mapped drive. It allows me to map a drive on my local PC for testing purposes, and then use the same drive letter on the production PC.

I've also noticed that if I try to open a project in VS 2017 in the same environment, but type in e.g., F: as the path, it doesn't recognize it, even though F: is a mapped drive on my computer.

I'm not running VS in Admin mode. What could be causing this?