The sample page does not apply to the text page
Please help me with this problem.
I imported text and created sample pages.

When I apply the sample page to the text page, the sample page is not taken to the text.
I also found that there is no text allocation icon (I don't know what it's called. I highlighted it with a red frame) on the text page.

On other pages, this icon appears as a sheet of paper with text and arrows. And on these pages the sample pages work well.

Please tell me how to activate this icon so that the sample pages apply to this text page. What am I doing wrong?
I really need your help. Thank you.
