No syncing over icloud

Hi.

I’m using Pages to write a book. I’m using an iPad Pro and a MacBook Pro. Up until now I have had no problems accessing my work in iCloud Drive on both devices but now the MacBook Pro doesn’t recognise files updated on the iPad and neither will the iPad recognise anything saved by the MacBook. I recently bought more storage on iCloud Drive. Could this be a cause of the problem? I’m using Pages 6,3,1 Mac OS 10.13.3 on MacBook and 11.2.6 on iPad.

Thankyou for any help.

Frank