Pages on iPhone won't open anything

I've got an iPhone X (iOS 13.2.3) with Pages 5.2.1 (Latest).

My documents are stored on iCloud. I can open and edit my documents on my iPad (iPad OS 13.2.3, Pages 5.2.1), and on iCloud.com with no problem.

But trying to open on the phone, it either says The file "whatever.pages" couldn't be opened., while more recent files give the message, Can't Open Document "File Name" can't be opened right now. Pages couldn't read the file. You can try restoring to a previous version.

I observed the updated document get downloaded on my phone after successfully updating from elsewhere, but the same error persists.

I reinstalled Pages. No change.

Any help would be appreciated.