Can't figure out how to accept family sharing invitation

I want to share my iTunes music with my husband.

I sent a family share invitation from my iPod Nano, which is my only Apple device, to my husband's Apple ID, which uses his gmail address.

We opened the message using the Mail app on his iPhone 12 and tapped "get started."

It takes us to Settings>iCloud> screen and nothing happens.

I already double-checked that his iPhone has an iOS and iTunes version newer than the minimum required in the sharing invitation.

What are we doing wrong?