Error Host not found (authoritative)

[Melimelo 0]

Hello
I use Gluetun on my NAS to connect to AirVPN and qBittorent as a client.
I regularly get an error with one tracker (and only with that one): "Host not found (authoritative)". I usually reset the Gluetun/AirVPN connection and changing server "clears" the error.
But sometimes this doesn't work. I can restart the NAS, reset the connection several times, but the error remains and I can't use the tracker.
I suppose there's a DNS problem, but which one? And why only with one particular tracker?
Thanks for your help.

Edited ... by Melimelo

[OpenSourcerer 1450]

Tell us the tracker.

[Melimelo 0]

I am currently communicating the information with technical support.