prepaid J1 visa esim

Good morning, I'm a foreign exchange student and the American Gov. provided me with a prepaid J1 sim card. Here in the US I've just bought a new Iphone 11 which requires me to use a eSim. I've been having a lot of issues understanding what to do since I've used the QR code on the T-Mobile site but it says it's expired. Please help me, I need to heat my family