Cannot Open Word Documents in Dropbox

Mega, thanks so much for your reply!  Here is a screenshot of the error message:

In the past, I have ALWAYS simply double clicked the Word file to open it in Dropbox.  That is when I now get the error message.  At your suggestion, I tried "Make Available Offline."   That alone did not open the Word document, but after doing that I was able to double click and open the Word document!  Thank you!  I previously never had to take the step of clicking "Make Available Offline."   Previously i could simply double click the documet and it would open .  This seems like a more tortuous path to take to access the document, but if that is what it now required then I'll do it! 

It appears that the documents that I open this way remain available offline unless i take the extra step to convert it back to Available Online.   Again, this seems like a tortuous path, but since I need to save space on my Surface Pro's hard drive it seems like a necessary extra step.     

Finally, after all my whining about torturous paths and extra steps, I have a very dim memory of POSSIBLY changing the Dropbox folders on my Surface Pro from "Available Offline" to "Online Only," again to save hard disc space.   That might explain why I must now take these extra steps that I'm describing?   

Thank you once again for your assistance!  I deeply appreciate it!  I welcome any further comments you might have about what I have written.

My best to you.