Why can’t I convert my pages file to PDF with the new update?

If you really meant iOS instead of macOS, then with the Pages document open, click the ⋯⃝ on the toolbar. That drop down menu will have an Export menu item and clicking that leads you to PDF.

On macOS, you would use the Pages File menu > Export To > PDF, or Pages File menu > Print… > PDF > Save as PDF.

Tap on the name of the document on the top left side of the screen. The Export option has been moved there.

Is this issue for Pages in iOS (iPhone and iPad) or for Pages on Mac?

What happens when you try to convert to PDF? Do you get an error?

How are you converting them to PDF exactly?

Had you stated iPadOS and not iOS, my response would have been more accurate.