I am running into an issue getting my two fully Unlocked Galaxy S20 5G's (SM-G981U1) to recognize and connect to a private 5G SA and LTE ENB/IMS network. I have a callbox set up that broadcasts the core network, along with its test SIM cards in both devices. I have the PLMN, correct APNs, and each device's IMEI provisioned properly. When the network is set to 5G SA mode, the phones recognize the SIM card with no issue but are not able to establish a 5G connection in any capacity. When checking the logs on my callbox, there is a registration request sent out by it that is never returned back.
Additionally, when I have my callbox configured to broadcast a LTE ENB network, along with IMS, the phones are able to recognize the LTE data network with no issue. However, they are unresponsive with the IMS network, and when looking at their SIM settings they list themselves at "Not Registered" for the IMS server.
Is there any way I can get a grasp as to why my devices are not successfully establishing either an IMS nor 5G SA connection?