can't copy and paste from pages to keynote

I'm unable to replicate this. I tried copy/pasting text from multiple Pages documents into both existing and new Keynote presentations and it worked as expected.

Therefore there has to be something specific to your environment. Is this true when copying from any Pages documents? or just this specific essay?

I still maintain there is something specific about whatever you're copying that's causing the problem.

How much text are you copying? words? paragraphs? pages?

Plain text or styled?

Does the text have embedded images, tables, or other media?

Can you create a new document, type some text, then copy/paste that?.

I agree with Camelot. Fundamentally, Pages is a word-processing application and Keynote is intended for presentations. There will be differences in their behavior during some copy/paste activity.

Let's take Pages and Keynote (version 14.3) on macOS as an example. Text boxes on Keynote are not the same as those in Pages. If I select a paragraph of text in Pages, click and pause momentarily, then drag that text clipping to Keynote, it is placed in an elongated, single-character height text box without any line or paragraph breaks.

Should I select all of the text (four paragraphs) on a Pages document, and copy and paste that into Keynote, then I still get the Keynote style, full-width Text box with four entries representing the individual paragraphs. This is somewhat annoying until one realizes that they can simply horizontally resize that Keynote style Text box to restore the paragraph formatting previously observed in Pages.

If I select a Pages Text box with the same paragraph of text in it, and then copy/paste that into Keynote, then the Pages style Text box is preserved in Keynote and appears as it did in Pages.

One can select a Pages table and copy/paste it into Keynote with a retained appearance and formulas as in Pages — unless that Pages table has other table dependencies in its formulas.

Tested: macOS Sequoia v15.3