Grandstream h813 + omnia 2020 voip

Good morning,
I have to configure VoIP on the Iliad network to use with the Omnia 2020, I have the Grandstream H813 VoIP splitter configured as per the guide https://www.iliad.it/docs/VoIP/Guida_Turris_e_VoIP.pdf
but the device doesn’t register, do I need to configure something on the omniA?
in case if I can load the screenshots, I can’t get it to work
can someone help me?
Thank you