When creating a topic about files that won't open, please provide us with a link where we can download them. The only way for us to check what casued the problem, is to analyse the files you're trying to open.
Go to your OneDrive online account
Browse to the folder or file that you want to share
In case you would like to share a complete folder with .dita and .ditamap files, click the Share button in the menu.
- In case you would like to share one specific file, right-click on the file and select Share.
In both cases, choose 'Get a link' and provide this link in your topic.