Updated Microsoft Office users, eagerly upgrading to the latest and greatest version of the company's productivity suite, have found that the venerable Offline Files function has gone, er, offline.

Judging by the increasing rumbling in the company's forums, the problem kicked off with version 1904 of the productivity suite and afflicts Office 365, 2016 and 2019. It manifests itself when a user has My Documents and/or the Desktop folders remapped to a server, but with Offline Files configured.

In that instance, when the PC is connected to the network, it should hit the server, but when out and about it would run from the locally cached copy. It's not an unusual scenario for businesses with mobile workers, even if Microsoft would much rather they used something a bit more modern like, say, OneDrive for Business or Windows Work Folders On-Demand.

Having been using the tech for years, users are now reporting errors along the lines of...

Sorry, we couldn't open '\\servername\fileshare\filename' because the server isn't responding.

... on attempting to open Offline Files when disconnected.

The sort of thing that could happen, for example, to a worker trying to open that all-important spreadsheet in Excel while on the move.

The issue appears to be solely related to using an Office application to open files. You can, for example, open an offline .csv file in notepad.exe OK, but try it in Microsoft's lack-of-productivity app and an error is vomited onto the screen.

Workarounds have included manually copying the files somewhere other than the offline location and then opening them, which defeats the object somewhat, or downgrading Office back to a version before the problem began – a painful scenario for administrators, particularly with regard to patching and updates.

And, of course, in the wonderful subscription world of Office 365, Microsoft really wants to keep that update train rolling. Even if those updates break existing functionality.

Interestingly, the problem appears to go away if the PC manages to get online, even if it can't actually "see" the server. It's only when a user is completely offline that the borkage occurs.

As the grumbling has increased, more users have chimed in, sharing such unheard-of scenarios as: "Our laptop users travel often and they can't work on their documents when disconnected from the internet," before observing: "This is crippling some of our users."

Microsoft has been characteristically tardy in responding. Some have fingered Windows 10's Windows Information Protection (WIP) feature, which comprehensively breaks Offline Files.

The workaround is to not use Office to open the file, or to stay connected. Or update to Work Folders or One Drive for Business.

Microsoft, you see, has no intention of fixing things, saying : "There are no plans to update Offline Files to support Windows Information Protection."

Users, however, claim that they are not using WIP, so either something else is happening, or Microsoft has quietly enabled the technology. We contacted the software giant to find out, but have yet to receive an official explanation.

The only clue is some text purporting to be from Microsoft support staff warning that "Office from [the] start was designed to be a single client Productivity suite" before explaining that the suite has "issues" with folder redirection and "Microsoft cannot guarantee that folder redirection will always work."

While the operative was aware the problem "will cause some inconvenience", it was all down to a design issue "that has not been changed".

We asked Microsoft if this was, in fact, the company's position, but again, nobody from the company's UK tentacle was able to confirm.

A Register reader got in touch to tell us that the tech had been used for years in his organisation, keeping desktop and docs stored on the server, but still available when offline. He observed: "All of a sudden, Office 365 files can no longer be opened if they happen to be on one of these synced folders."

While admitting that "the offline files and folder redirection is pretty poor technology" – something anyone who has had to rebuild the offline cache would agree with, he added: "But to stick it to the businesses that rely on the technology in such a brutal way without warning seems pretty underhand."

Arbitrarily breaking Office functionality isn't a good look for Microsoft. Some users simply cannot migrate to the likes of OneDrive for compliance reasons, while others would prefer a little more notice that a function was simply going to stop working.

Or at least a definitive explanation when it does. ®

Updated to add 11/06/19

A Microsoft spokesperson responded: "We recognize and value the faith that customers place in Office for reliability, so we always aim to notify customers with ample time about any feature deprecations. This feature has not been deprecated and we are investigating the issue. We regret the impact to customers and will make sure to inform them of available fixes once we've identified the root cause and steps to resolve the issue."