Hi Kamil,
i dont know if this is your specific case, but based on genesys document on carrier interoperability (https://help.mypurecloud.com/wp-content/uploads/2020/11/Genesys-Cloud-Carrier-Interop-Spec-2.0.pdf), the SIP REGISTER method is not supported (par. 2.5.2).
Also in paragraph 2.9 it is explicitly stated that: "Registration is not supported on Genesys Cloud trunks. Genesys Cloud will not register with the Carrier and will not accept registration from the Carrier under any circumstances."
I hope this has been useful.
Regards
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Matteo Paratici
NTT Data Italia S.p.A.
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