Draytek Vigor2860 Series User Manual page 551

Also you will get a Tracking Window if you don't block the pop-up window.

Don't setup a user profile in User Management and a VPN Remote Dial-in user profile
with the same Username. Otherwise, you may get unexpected result. It is because the
VPN Remote Dial-in User profiles can be extended to the User profiles in User
Management for authentication.
There are two different behaviors when a User Management account and a VPN profile
share the same Username:

If SSL Tunnel or SSL Web Proxy is enabled in the VPN profile, the user profile
in User Management will always be invalid for Web authentication. For example,
if you create a user profile in User Management with chaochen/test as
username/password, while a VPN Remote Dial-in user profile with the same
username "chaochen" but a different password "1234", you will always get error
message The username or password you entered is incorrect when you use
chaochen/test via Web to do authentication.
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Vigor2860 Series User's Guide