OCServ won't respond to any UDP port

Description of problem:

I have tried port 443 and many other port numbers.

Version of ocserv used:

OpenConnect VPN Server 1.3.0

Client used:

OpenConnect VPN graphical client Version 1.6.2 for Windows 64 bit

Distributor of ocserv

Compiled from source

How reproducible:

Try to connect with UDP enabled.

Actual results:

2025-03-27 16:36:36 | 71bc | DTLS handshake failed: Resource temporarily unavailable, try again.

Expected results:

DTLS to be successful.