Work through these in order:
Has the invite expired? Invites last 7 days. Expired ones show Expired — resend to renew in your family list. Resend it.
Did they open the link you sent? If they downloaded the app and signed up from scratch, they may have created a new, empty family space of their own. Ask them to open your invite link while signed in, or send a fresh invite.
Was the whole link copied? A link cut off in a text message won't work. Use Copy link or Share a link rather than copying by hand.
Are they using the same account? If they accepted with one email and are now signed in with another (or with Google instead of email), they won't see the family. Ask them to sign in the way they accepted.
Was it a perspective invite? People invited to one loved one's story only see that story, not the whole family space. To give them full access, invite them to the family.
Do they have Can view access? Viewers can see stories but can't add to them. Change their role from your family's member list.
Still stuck? Contact us with both email addresses and we'll sort it out.