I installed OMV on a Raspberry Pi 3 and it seems to be functioning fine except I am unable to write to the shared drive from my Windows 7, 64 bit PC from my original user account. I can see it and read files but cannot write to it. Originally I could not even open the file. I had to add a Windows password first. The account previously did not have a password since it is my home PC used only by myself and my wife.
I get an Access Denied message. I attached a screen shot.
I added a new user account and that account can see, read from and write to the folder. As far as I can tell the permissions are exactly the same on both accounts in OMV.