Hello, Brittney1999!
Thank you for using the Apple Support Communities!
I see from your post that you're not able to redeem your iTunes gift card, and when you try the iTunes Store freezes up and gives a loading screen with a spinning wheel that doesn't go away.
Do you get any kind of error message at any time?
Have you tried restarting your Apple device or trying another device with iTunes to redeem the gift card?
After restarting, check to see if the funds have been added to your Apple ID.
If you try again and the issue persist, I recommend that you contact Apple Support. As noted in the article, If you can't redeem your App Store & iTunes Gift Card, Apple Music Gift Card, or content code:
"Apple Support can provide help, but you might still need to contact the retailer the card was originally purchased from.
Please be prepared to provide:
- An image of the full front and back of your card.
- A sales receipt showing when your card was purchased.
- The serial number from your card. "
Kindest Regards.