Why can't I save Word files on USB flash memory?

[AC Question]

I'm not sure if this is a problem with Android or Microsoft. I have an Asus ZenPad10 with Android 5.0.1 and Microsoft Word app. I can access the files on my usb memory but when I try to save the changes (or save a completely new file) on that memory I get the error "You can't save here. Please choose another location." Is there anything I can do to save files on the external memory? Using clouds is not an option for me.

 

[Feldon]

Kitkat (4.4) and Lollipop (5.0) interfere with writing to SD cards. This may extend to external devices. You may need to save the file to internal storage and then use a file manager to move the file over to the USB stick.