Error in mounting share (115) => Volumio2, RPi3, Fritzbox NA

Hey folks,
I am new to the Volumio and Raspberry Pi world, but already quite enthusiastic and wanted to say thanks for your great work!
I need some help with mounting a micro SD card, which is set up in a Fritzbox fon WLAN 7390 as NAS storage. I can easily access it both from Linux Mint and WIndows 10, but volumio says:

"Error in mounting share xy (115): Operation now in progress Refer to the mount.cifs(8) manual page (e.g. man mount.cifs)

You can see my settings on picture 2, I also tried leaving options field empty but same problem.

Can anyone tell me what I am doing wrong?

under Linux you have to use the normal slash “/” instead of backslash “” under Windows.

I had problems too to mount Fritz - look there: failed-mounting-fritz-nas-volumes-t7225-20.html