Hello amy_b84,
Welcome to Apple Support Communities!
We want to help you get this child account created, let's make sure you're using these steps:
"How to create an Apple ID for your child
Children under 13 can't create an Apple ID on their own. (This age varies by region.) But if you're the family organizer or a guardian, you can create an Apple ID for your child.
On your iPhone, iPad, or iPod touch
To verify that you're an adult, you need a credit card. On your iPhone, you can also use a driver's license or state ID added to Wallet.
In iOS 16 or iPadOS 16 or later
- Go to Settings > Family.
- Tap the Add Member button .
- Tap Create Child Account, then tap Continue.
- Enter the child's name and birth date. Be sure to enter the correct birth date — you can't change it later.
- Follow the onscreen instructions to finish setting up the account. For your child's Apple ID, you can use their email address, the suggested @icloud.com address, or their Game Center nickname."
This Apple Support page has the full details: Create an Apple ID for your child - Apple Support
If the issue remains after these steps, try restarting your device and testing again.
You can further isolate the issue by testing while connected to another Wi-Fi network or with another device.
We hope this helps to get the account created.
Cheers!