Permissions
Something is refused, or a page is not in the navigation.
"You do not have permission"
What a member may do is decided by their role — Roles and permissions. A client is read-only by construction; a user works on sites but does not manage the workspace; an administrator does everything. Ask an administrator to change the role, or to do the action.
A page is missing from the navigation
Pages are shown only to roles that may use them. Team, workspace settings and billing are administrators' pages. A client sees only sites, and only the sites of the clients they are attached to — a client attached to no client account sees nothing.
An invitation was not received
Invitations are sent by email to the address entered; check the address on the Team page and the recipient's spam folder. An invitation is accepted by signing in or registering with that address.
The API returns 401 or 403
401 is no key or an invalid one; 403 is a valid key that may not do this. Keys are created and revoked under workspace settings by an administrator — Authentication.
The site refuses the platform
That is a site-side credential, not a dashboard permission: see Connection problems.