Dropbox can't see mounted drive

Hi, I just installed Zorin Pro 16.1 on my desktop. Dual Boot with windows 10. The Zorin installation is on a separate hard drive. I use Dropbox a lot, so I installed it in Zorin. However, my Zorin system disk is kinda small, so I want to move my Dropbox folder to another unused HDD on my machine. I mount the drive successfully, but when I go to Dropbox settings to change Dropbox location, the drive does not show up, i.e. Dropbox does not see the mounted drive.
Any suggestions?
Thanks