Why can't my teammate see a page or tab?

Each role only opens the parts of the dashboard it needs, so a missing tab is usually the role. Front desk doesn't edit the site, designers never see leads or customers, viewers can't change anything, and only the owner sees Billing and Add-ons.

If they need it, change their role in Settings → Team. If they can't get in at all, make sure they're signing in with the exact address the invite went to; an invite works once and for 7 days, so click Send again if it ran out.