Initially I received an error that FIND: Parameter format not correct. I'm not sure what changed, but now when I look at *Messages* all it tells me is: Aborting an helm session running in background (I'm using helm-projectile). This happens even when I run helm-projectile immediately after opening Emacs.
What's your repo type? Do you have gnu find installed?
Had the same Problem you need to install gnu findutils and put C:\Program Files (x86)\GnuWin32\bin at the top of your PATH variable. And then of course close emacs and start it again (no restart) to get the new PATH in emacs.
A better fix for this would be using the value of the find-program variable in projectile-generic-command, this way, you can customize the find program that's used for all emacs find calls at once.