The only difference that I can see between this client’s workspace (3 websites) and my other clients’ workspaces is that I seem to have been added as a Seat on this one.
There is this which might be useful though: of the 3 websites this client has, 2 have paid hosting (Business Plans) and 1 is on the Starter Plan. When I open the one on the Starter Plan, both the checkmark and the history icons are visible. Also, when I paste in a Relume component, there are no errors. However, it might be worth bearing in mind that this website is not Client-first.