VPN access using L2TP/IPSEC stopped working on SMC d3g router
I have been using both pptp and l2tp to connect from a remote location into my office network, through an SMC d3g comcast router. No setting changes have been made to it, yet L2tp just stopped working sometime during the last week of november 2019. PPTP still works fine.
I have investigated this throroughly by using different remote computers, and contacting technical support of my server machine for additional assistance (no server issue was found). I can connect to the L2TP server through a computer on the internal network without issue. So something on the router or internet is blocking the connection of this protocol (ports 500, 4500, 1701).
In addition, I use remote wake on lan (using port 9) to remotely power up a computer on the internal network, which also stopped working recently. However it does work when I am internal to the network.
What can I do to fix these issues, or is comcast blocking these services?