Open new windows as tab not working?

I had a standalone built using Mac 10.14; LC 9.03. Sonoma broke the menus (actually the app would not even open) so I upgraded LC to 9.6.10 and that solved the menu problem. However now a user is reporting and I have confirmed that the option to open new windows as a tab in the existing window

Open new windows as a tab not working?

I had a standalone built using Mac 10.14; LC 9.03. Sonoma broke the menus (actually the app would not even open) so I upgraded LC to 9.6.10 and that solved the menu problem. However now a user is reporting and I have confirmed that the option to open new windows as a tab in the existing window