I have a SIM card from SORACOM, and seems to work fine when I use it with a 4G module. However, when I try to use it with the EM9191 with this USB adapter (USB3 to M.2 Key B 4G 5G Modem Adapter Enclosure with SIM Card Slot - V7 - Sierra Quectel Fibcom SimCOM 5G Supported), I am unable to connect to their network. I am testing it using a Windows machine, and it does show the SORACOM cellular network but it does not connect. After reaching out to SORACOM, they suggested to check if the EM9191 support roaming SIM cards. Thanks.
What firmware and carrier PRI are you using?
What is the return of