Hello,
Thanks for writing. This is because you are using Android 4.4+ (Kit Kat). Google has removed global write permissions for 3rd party apps (like F-Stop) on SD cards (internal memory works as expected). We do have a workaround we implemented in v3.1+, but it does not work on all devices including the S5 and some Xperia devices.
There isn’t really much we can do. You can use internal storage or try rooting your device, which may help on some devices.
Here is some more info:
http://lifehacker.com/android-kitkat-blocks-some-access-to-micro-sd-cards-1524997895
Regards,
Jason Seelye
