Thanks for the quick response and suggestion Mark. I was on the latest stable version, but I uninstalled it and installed the latest Beta and still ran into the same error. I've attached it so you can see. I have a 200GB SSD card in my micro-SD slot in my Surface Book that I'm trying to move my Dropbox folder to since I have so little space left on my laptop hard drive.
While Dropbox will allow you to use an external hard drive, it will not allow you to use a removable drive such as an SD card, flash drive, etc. There are workarounds (search the forums), but they are not supported and highly not recommended.