Try killing Delta Chat and restarting it, it likely remembered that the relay has no TURN. This is remembered for 7 days, so after 7 days without restarting Delta Chat will try to request it again.
I tested that the TURN server is indeed available:
? GETMETADATA "" (/shared/vendor/deltachat/turn)
* METADATA "" (/shared/vendor/deltachat/turn {58}
sediz.iosa.it:3478:1761762241:mUlsxZ1KjP5XbxEoGiydSwsgoHk=)
? OK Getmetadata completed (0.002 + 0.000 + 0.001 secs).