I have recently moved across the country and need to use my workplace VPN (L2TP/IPsec with pre-shared key), during the move i reset my router and updated firmware.

I set up the VPN using company guide and it worked great, for about a week.
Since then, I have been unable to connect (Windows states connection cannot be established)
Nothing was changed on the router between VPN working and not working.

Fairly sure my router is the problem, as I have tested with three PCs and all can connect if they're plugged directly into my fiber modem, or connected to my phones WiFi Hotspot, but none can connect when going through my router with either cable or WiFi (nor if connected to phone hotspot while phone is connected to router), likewise VPN stopped working on all machines at the same time.

I have tried:
Restarting the router.

Ensured router's own VPN server is not running.

Disabling Access Control

Disabling DoS Protection

Disabling SPI Firewall

Disabling Antivirus

Disabling QoS

Disabling Print Server

Various configurations of enabling/disabling PPTP/L2TP/PISec Pass-through and ALGs

Changing MTU Size

Putting machines in DMZ


I have no virtual servers, Port Triggering nor static routes set up.



Does anyone have an idea of what could be causing this?