I would maybe try and delete the QVPN software from the PC and then install it again on the PC and then regenerate
the certificate on the router. Make sure that you are using the latest version for QVPN. I have seen this correct the problem that you are
describing. Also make sure to check the firewall setting on the PC that you are trying to VPN into. Make sure the firewall is turned off on the PC.
THANKS