pages won't open documents

All files in a Save/Save as dialog are greyed out as you cannot open them from that dialog. In a File chooser dialog, only documents in a format that Pages can open, and on a compatible filesystem will be selectable. For instance, I am looking at a Pages v12.1 File Chooser on macOS 11.7, and PDF documents and images are grayed out, but Pages documents and files containing text are not.

What type of document are you attempting to open and is it on your local drive, a mounted share from a Windows server, or some Cloud service (e.g. Google Drive, Dropbox, Microsoft OneDrive, or Apple's iCloud, etc.) to name a few?