kernel: [640598.637783] No dialect specified on mount. Default has changed to a more secure dialect, SMB2.1 or later (e.g. SMB3), from CIFS (SMB1). To use the less secure SMB1 dialect to access old servers which do not support SMB3 (or SMB2.1) specify vers=1.0 on mount.
Aug  2 22:12:19 kernel: [640598.642602] CIFS VFS: cifs_mount failed w/return code = -22

This is a currently a bug in Samba or the Kernel but you can easily work around it by adding vers=2.0 to the mount options, either in /etc/fstab or if using mount manually, by using the -o vers=2.0 option. This forces Samba to use SMB version 2.0 which does not have the bug.

-o vers=2.0