Seems that some users have been reporting that the 4 options under
Advanced/Firewall/ALG do not come with check marks and are disabled by default out of the box. This seems to be causing some problems with some connections using VPN and some voice services through the router.
For those encountering this problem, please review these settings check mark to enable
ALL 4 options. Then
save the setting and let the router reboot. These should be enabled by default anyways.
Test the specific service again. It should work well.
Reminder: Save the current routers configuration to file under
Tools/System after making changes to the routers management page.