Nextdns not working with mobile data

On my smartphone, Nexdns is configured and functioning perfectly with WiFi , my private dns being 485c14.dns.nextdns.io

switching  to mobile data, breaks everything as my phone cannot find
485c14.dns.nextdns.io ip address.

Ping 485c14.dns.nextdns.io gives
... Unknown host 485c14.dns.nextdns.io

Not sure this is a nextdns issue, anyway it would be very appreciated if  someone could  help me getting software working right with mobile data.

My phone is a xiaomi with android 15 and hyperos 3