Installing an eSIM does not always select it for mobile data. Check this before testing the connection.
iPhone
Open Settings > Cellular or Mobile Data > Cellular Data or Mobile Data, then choose the SimFuse line. Enable that line if it is off. Consider turning off Allow Cellular Data Switching to prevent fallback to another line while troubleshooting.
Android
On Pixel, open Settings > Network & internet > SIMs and choose the SIM for mobile data. On Samsung, look under Settings > Connections > SIM manager > Mobile data. Turn off automatic data switching or backup data on the other SIM where that option is available.
Check the result
Briefly turn Wi-Fi off and open a small webpage. Match the line's ICCID with SimFuse if labels are unclear. See "Find your ICCID or EID".
Keep roaming off on the home line unless you intentionally want to use it and understand the charges. Selecting the travel line for data does not by itself prevent home-carrier charges for calls or texts.
If the correct line is selected but data still fails, see "Turn on roaming for your SimFuse eSIM".