This issue came up with a client who was connecting remotely to a Draytek Vigor device – other users were able to connect successfully. Checking the version of the router software showed it was fairly recent. On observing the laptop with the problem I noted two things – 1) the draytek smart VPN service was not running and 2) a black dos screen was very briefly being displayed when the client was being launched.
The message displayed on the dos screen was
“Hello, Detecting services action. Hello, this message dialog indicates that the “SmartVPNClient.exe” is asking permission” from computer. Thank you for waiting patiently.
If you restarted the vpn service and then tried to start the client – the service would be stopped! So I tried another PC and installed a fresh copy of the vpn client from here and noted it was version 5.3. Checking with the user I discovered that the client might not have been used for some time. Removing the 5.1 version and replacing it with 5.3 cleared the issue and I was able to establish the VPN correctly and test access to resources behind the firewall.
So if you see the flashing dos screen when launching the SmartVPN client (you may see it but its hard to read the tesxt) – perhaps it time to remove and install a more current version