Hello, I previously responded to you via Discord (I'm not sure if you saw that there or which came first).
That message is originating from the custom theme you are using and is unrelated to FOSSBilling itself. I don't know why Tide was updated to have that message, however the text "This page is obsolete" does not exist in FOSSBilling itself and only exists in Tide.
You should report the issue to them so they an resolve it on their end