Some of the documents in the Files app on IPad can not be opened
I have a number of folders in the ICloud Drive/Documents of the Files app on my IPad Mini.
this is my problem:
For some of these folders I can open them, see the title of the items inside, click on the one I want to read and it opens right away.
But for some other folders, when I click on the item I get this:
And if I click on preview I get this:
can somebody please tell me what to do to fix this?
thanks.
iPad mini, iOS 12