Unable to download apps on child’s Apple Watch

We bought an Apple Watch for my son and set it up under his own Apple ID using family setup from my iPhone. He is too young to have an iPhone of his own. We have various parental controls in place through Screen Time. The watch works but we are unable to install apps using the App Store on the watch. We can browse the App Store and click “Get” to download an app, enters his passcode, then his Apple ID password, but then the app fails to download. It just goes back to the app screen where he clicks “Get” again, and goes through the same loop. We did try disabling the “ask to buy” option under family sharing, but this did not change anything. I cannot install apps using the Watch app from my iPhone, because this is not an option when using “family setup.”

We have verified the apps we are trying to download do not require an accompanying iPhone. We have tried a work around by downloading the apps to our iPhones and trying to download them on his watch with Family Sharing, but they do not show up. We also verified it is not his Screen Time restrictions.