Hey there @SuzieQuize Thanks for reaching out to us. Did you verify on our website, if the device is compatible with our service? Link: https://www.boostmobile.com/bring-your-phone.html?intnav=TopNav:Phones:BringYourPhone.
If you're using a cellular data connection, connect to a reliable Wi-Fi network instead.
If you get an error message on your iPhone that says the activation server is temporarily unavailable or cannot be reached when trying to activate, wait a few minutes, then repeat the steps above.
If you still can't activate your iPhone, try again using your computer instead. Here's how:
Make sure that you have the latest version of macOS or the latest version of iTunes.
Check that your computer has an Internet connection.
With the cable that came with your iPhone, connect your iPhone to your computer. Locate your device on your computer.