I've had 32-bit Office 2016 installed on this Win 10 64-bit system for quite a few months with no issue. This behavior started recently. Possibly with the latest Windows or Office update? I'm unsure what the trigger was. But all updates are applied.
Neither Excel or Word will open a file in Protected or Read-Only mode. It's easiest to show this by shift-right-clicking a file and trying to open in that mode explicitly. For "Protected Mode" Excel says "The file is corrupt and cannot be opened." while Word says "Word experienced an error trying to open the file." "Read-Only" mode results in the files opening normally for editing.
This happens to all Word/Excel files. Note that the files open as expected when opened normally for editing. And Excel/Word seem to behave as expected when open for normal editing.
Additionally, the Outlook preview viewers for Word and Excel are broken. When trying to preview an Excel file it briefly says it's opening the Microsoft Excel previewer, then says that this file cannot be previewed because no previewer is installed for it. Curiously, the file previewer for Excel works in File Explorer when the preview pane is open. I'm pretty sure this is the same previewer as Outlook tries to use.
I have repaired, and uninstalled/reinstalled Office. I have verified that DCOM is enabled and the default authentication and impersonation are correct. I have verified the registry entries for the previewers, and the previewers in Outlook are enabled and selected. Yes, I know how to bypass Protected/Read-only mode, but I'd like to have it work as designed.
Anybody have any ideas what might be going on?