@David-TP thank you for prompt feedback. I forgot to mention that when it stopped working, I tested it on my old wifi router and that worked. So I have tested back to back and sadly this Wi-Fi router...

I am experiencing the exact same problem as https://community.tp-link.com/us/home/forum/topic/203410. Since last 3 days, VPN stopped working for unknown reasons. I updated the firmware after it...