In fresh Magento 2.2.0 installation
When import product from csv file error triggers as "Sorry, but the data is invalid or the file is not uploaded."
Can you share the file you've used?
Can you check your file?
It seems there are some characters issues?
@Damian Culotta sorry for the late reply.
I reinstalled the Magento and when i tried using the same file it worked, guess it's some kind of permission issues which i messed up earlier.