Under Account settings/ Integrations I've changed the defaults for Word & Excel to open with Microsoft Office Online but the file still open with box previewer.
This is happening on macOS Sonoma and Sequoia / Safari / Chrome / Edge.
I've tried this across three machines with and without box tools.
Things I have tried.
1.Clean MacOS
2. Different web browsers
3. files have the correct suffix .xlsx and .docx