Cannot open Pages files on my iMac

I had the same problem with both Numbers and Pages - followed a tip on Numbers community (to hold shift key when opening app) and Numbers now seems to be working normally.

I can open Pages from the launcher and create a new doc but cannot open any of the docs saved on my iMac (including the new one just created) - the menu bar greys out even though the app is still showing as open in the dock.

I have dragged a Pages file from my desktop into iCloud and can open it there both on my iMac and iPad.

I am running El Capitan OSX and Pagers 5.6.1 since November without any other problems.

Any ideas would be gratefully received.