Indesign 23 page numberiung: can't change page panel options

Hello. I am working with a document (digital only). It's an update, so it's been worked on before (not created from scratch). 

I want to update page numbers in Numbering and Sections, but it is not easy nor intuitive (I worked with Indesign and such for years and years). Bear in mind this is the version with 'Create Alternate Layout'/'split window' features which I never feel good about as saw some disparities. But that's just context.

The document has a page or two of A4 portrait, then, due to the nature of it, they want landscape pages inserted, for charts. Then back to prortrait. Two different master pages involved but eirther way, when I try to number the pages in the panel, it won't stick, even when I try 'Start Section'.

I basically want to make page one '1' then the rest follow (1 2 3 4 etc), but I can't make this happen.