You can check this quickly in your phone settings:
On iPhone: Go to Settings > Mobile Service. You should see your Yonder eSIM listed under 'SIMs'—make sure it says 'On'.
On Android: Go to Settings > Network & Internet > SIMs. Tap your Yonder eSIM and ensure the 'Use SIM' toggle is switched on.
If it's on, you should see signal bars or a network name at the top of your screen.