Sorry there was a problem and we can't open this document....

[Ian Moran]

We had an issue this week where users accessing the same set of documents were receiving the error ..

"Sorry there was a problem and we can't open this document. If this happens again, try opening the document in Microsoft Word"

This error seems more related to an on premise installation of the Office Web Apps server but this is Office 365 and SharePoint Online. It also seems somewhat transient in that it disappeared eventually.

Mandatory checkout is not enabled on the document library

Any pointers to troubleshoot ?

[#2]

Take a look in the O365 Admin Center for any messages about service problems.

[#3]

I did, there were none relating SharePoint at that time.