portfolio won't let me add a photo grid to existing page

hi,

i may have forgotten how to do this, i've searched online and can't find a solution.

i've clicked on the '+' but a grid is not an option.

i recently went to update my adobe protfolio after a long time and noticed I can seem to add phot grids to my existing page.

i'm running OS10.15.7 and using firefox 112.02.

here's a screen shot of the dialogue window.

i'm grateful for any help.

thank you.