Pages Sharing button greyed out / not working...

I'd appreciate anyone's help on this.

On the Pages menu screen with the grid of icons showing your documents, there are options to Share, Copy and Delete when you enter the editing screen.

The only documents that allow me to Share are ones from a long time ago. All my recent documents have a greyed out Share button. I can open the documents and chose to email it from there (the Spanner button), but it's laborious and clearly isn't the way the App is supposed to work.

I have deleted and redownloaded the App to see if that fixes it.

Any ideas?

Thanks in advance.