I have exactly the same problem with my NetDrive (2.6.20 build 985).
From one day to the next, it doesn’t work anymore: ‘Connection error’.
I have changed nothing, either on the computer, the DiskStation nor the network.
Even on my desktop in the same network with the same items in the Options it works still without any problems.
I wanted also, as described above, produce a logfile. But in the Options I can only change the Log Level from ERROR to DEBUG, but there’s no VERBOSE.
So no logfile is generated.
In the synology DS I have nothing blocked.
What can I do to reuse Netdrive?