Cifs mount error(56): Invalid request code

Question

I am trying to cifs mount my Arch server (called server) to an SMB disk on a router (experia). This keeps throwing me error messages. Invalid request code.
So I decided to test this on my Arch client (called kastje). Same issue:
[david@kastje ~]$ sudo mount -v -t cifs //experia/testshare /mnt/temp -o username=testuser,password=testpass
mount.cifs kernel mount options: ip=192.168.178.1,unc=\\experia\testshare,user=testuser,pass=********
mount error(56): Invalid request code
Refer to the mount.cifs(8) manual page (e.g. man mount.cifs)
However, mounting through gvfs-smb (PCmanFM) works fine, so it seems that both my client and the router are configured correctly but I am failing at using mount.cifs. But I just cannot find out what. Searching for the mount error(56) turns up some result but none are really helpful, as they do not solve the issue .
I hope someone can point me in the right direction.

Answer 1

From my fstab:
//Server/Shares /mnt/Shares cifs guest,uid=1000,x-systemd.automount,iocharset=utf8,file_mode=0777,dir_mode=0777 0 0
//Server/Homes /home/pat/Server cifs credentials=/home/pat/.smbcredentials,x-systemd.automount,iocharset=utf8,sec=ntlm 0 0
Does your router have a smb.conf? Or, I should be asking, is a samba server running on your router? You may find that an NFS share might work better than samba, especially if you don't have a setup like mine.