insert-section break option is not available in Pages 5.5.2. What should i do ?

You need to click in the Text (default area not text in objects) to Menu > Insert > Section Break.

Peter

I am also having this problem, but the section break command is grayed out, so I can not use it.

You can not have a Section Break anywhere except in a WordProcessing document default text area as I said.

So where is your cursor when you try to insert?

You need to tell us exactly what you are doing, we can not see your screen.

Peter