Do you have access to A360?

You can try and make edits to your clients files there. Or have your clients try and save their files down  

In addition you can look to the following links to see if this can be helpful for your problem; 

• Error: The drawing file cannot be opened because it was created with a more recent version of AutoCA...
• Forum thread: Opening of new version of autocad files in older version of autocad

Sarah Emmsley
Technical Support Specialist