So, my Mikrotik router is behind my ISP's modem. I have set up an OVPN server, enabled Cloud DDNS, but my Android client cannot connect.
No error logs in Mikrotik, nothing, just connection timeout on my phone.
I tried almost everything, tried different ports, tried different configurations in RouterOS, opened ports in the ROS firewall and nothing.
It seems that my ISP's modem is blocking incoming connections, that aren't responses initiated by my IP.
I also have a local LAN bridge in ROS, but I am unsure if I can bridge the router and the modem. I do not have access to the modem, but I observed that when I delete the local bridge in ROS, I have differently named LAN connection which is not the same name when I connect directly to the modem via LAN.
Also, my modem is responding to pings, so maybe ICMP tunneling could be setup?