Check your OS configuration in system settings. There is one related to printing in Country/Region, Language, tab Other (description valid for KDE; I can’t check in GNOME on the current laptop because it has no printer configured). Sometimes the Page size in not in sync with the locale and must be forced to A4.
Verify (in the OS) your printer default configuration.
In LO, Tools → Options → Language Settings → Languages, make sure the Locale is the right one. If correction needed, exit LO after correction and reenter before next step.
Look for page size in page style Default Style. If it is not A4, then correct the default template. Search this site for how to.
Hope that helps