For those having issues adding the prepaid card to their mobile device, here's the best workaround until the fix for the Evo LTE is released:
Credit: FIX for google wallet activating - xda-developers
1) Change your device ID in your build.prop file to reflect the following
2) Reset Google Wallet
3) Reboot and re-enter your info in the Google Wallet app
4) Add your prepaid card
Done and done, your balance should show. If you're a newbie, $10 instantly. If you've already added funds, it should reflect your current balance.