I have a Samsung Galaxy Note 1.0 (2014) and want to log into an already existing Dropbox account which I can access from my desktop or phone, BUT....on my Galaxy Note it always shows an error at the top: Please enter a valid email address. I have entered it dozens of times. It doesn't change. I tried disable Dropbox, reboot, enable and still Dropbox will NOT accept my email address. Must be some secret trick nobody is aware of.