more tag don't work(read other issue already)

Dear All,

I trying to use more tag on my wordpress. but it don’t work.
I go to view as html it shows fine on HTML with <!–more–> when I replace <!–more–> as <!–nextpage–> it works. It can show on next pages.

These post is on front page I reload it and see it on website with preview.

Is there any other setting or thing we can do to make it works?
Thank you very much.

BR. Thomas