Permission for child’s account

Help!  I can't seem to give my child permission to sign in.  I sign her in, it takes me to a window that says grant permission, I click on the bubble that gives her permission then it takes me to the email sign in page again, so I sign her in and it takes me right back to the page to grant permission.  I've also tried the email request version and copied the link to the search engine and it takes me right back to the dialogue window to grant permission all over again.  I'm at my whit's end.  I've tried everything.  What am I doing wrong?