Port 1194 is the IANA-registered port for OpenVPN; the default is proto udp. On networks that block UDP, OpenVPN often runs over TCP on port 443 – slower (TCP-in-TCP), but it passes almost any firewall.
Open it inbound on a VPN server. With tls-crypt the server only answers packets with a valid key, which makes scans and DoS harder.
Typical: tunnel is up but large packets stall (MTU – mssfix 1400 helps), or TLS handshake failed because a firewall drops UDP 1194.
Check
sudo ss -ulpn 'sport = :1194'