I have a Samsung Galaxy S8 SM-G950U that I used with Verizon. I moved to Japan and got a Japanese SIM card through SoftBank and used in my Galaxy S8 without a problem. My account has a global roaming service included. I came back to the US with the Japanese SIM card and was told it would work in the US but it is not connecting to a network.
'Settings' > 'Connections' > 'Mobile networks' > 'Data Roaming Access' is on.
'Settings' > 'About phone' > 'Status' > 'SIM card status' shows "Network not available" even though I have 4 bars of signal strength. Also "Not roaming" is shown but I assume I would be roaming since I'm outside of Japan.
I called a support number and they told me to go into "SIM App" to update the SIM card but I cannot find this app or setting. If I search for "SIM App", I get a result in 'Apps' > 'App info' > 'Sim App Dialog' but my only option there is 'Force stop'.
I can connect to wifi but I would like to be able to connect/use mobile data when wifi is not available.