A few months ago i stopped using OnlyOffice because the app was not saving the changes in the .xlsx and .docx files. The changes were visible only in Nextcloud. Any info if this issue has been solved?
You might want to open a own thread about this. But check the logs, and check if allow_local_remote_servers helps (also see Changes made in Onlyoffice are not Saved to NextClound (actual) files · Issue #547 · ONLYOFFICE/onlyoffice-nextcloud · GitHub)