Problem

Error

You attempt to install a new patch for your Office Online Server (OOS) instance, and then experience this message prompt after you launch the installation:  

Error message

Security update for Microsoft Office Online Server (KB4011027à 64-bit Edition
The expected version of the product was not found on the system.

You made sure to download and install the very latest patch.  You verify that the patch is in fact for OOS and not OWA or some other software product.  From previous experience as a SharePoint Administrator, you do a quick search to see if there might be a OOS service pack that needs to be installed first, but you find nothing. 

Solution

The solution to the problem is in understanding the new approach Microsoft has taken to software builds and patches for its OOS product.  As an experienced SharePoint administrator, you understand that patches (software updates) are version-specific.  A software update for SharePoint 2010 only works for 2010 and not for 2013, 2016 or 2019.  So, you are used to patches being associated with version. Well, for OOS, patches are associated with builds.

Since its initial release in May 2016, Office Online Server 2016 has issued four new builds of OOS:

Build Availability Date Support End Date
16.0.6814.2226 05/04/2016 11/18/2016
16.0.7601.6800 11/18/2016 04/18/2017
16.0.7766.8550 04/18/2017 11/08/2017
16.0.8471.8525 11/08/2017 11/30/2018
16.0.10338.20039 11/30/2018 TBD

Source: Office Online Server release schedule

So let's say you installed OOS to a single server for your SP2016 farm, and the build number for that version is 16.0.7766.8550.  You then download what you believe is the latest patch, let's say it's the December 2018 CU for SharePoint 2016, or kb4011027.  This update won't work for your current installed build, 16.0.7766.8550, but for build 16.0.10338.20039 released 11/30/2018, just a couple of weeks before the update you are now trying to install.  If you nevertheless attempt to install it, you will experience the message prompt shown above.

This new approach to software releasing and updating introduces some wrinkles into our normal update routine.  It means first and foremost that we will need to track OOS build numbers and engage them like version numbers when engaging software updates; and this in turn means that we will need to perform OOS uninstallations and new installations at a higher frequency than just for version updates.  Review the release schedule above: if you deployed OOS when it was released, just to keep up with being able to install security patches alone in a timely manner, you would have had to perform four repetitions of OOS software un-installation and installation over a period of just two years.  This is a significantly greater upgrade administration effort than for the three-year upgrade cycle we've experienced for previous SharePoint versions, and this will need to be communicated to team leads and managers. 

Summary

If you experience the message prompt, The expected version of the product was not found on the system, when attempting to install the latest OOS software update, check what the build number is of your current installed OOS, and then compare it with the OOS release schedule to ensure that your current installed build number is the latest.  If it isn't, you must first un-install your current build and install the latest build before installing the latest software update. 

References

Notes

  • tbd