Microsoft Office won't open since updating Windows? This company has fixed it

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Since a cumulative update to Windows was released earlier this month, some antivirus software may be preventing users from opening Microsoft Office applications, including Outlook.

This is the case for Trellix, whose Endpoint Security Agent's Exploit Guard module blocked Office and some other third-party apps from running.

Microsoft says that other security software may also prevent Office from running since the update. Windows 11 21H2/22H2, Windows 10 21H2/22H2, and Windows Server 2022 are among the versions affected.

Google Chrome also blocked

"This issue only occurs with 32-bit apps running on 64-bit Windows with Trellix Endpoint Security version earlier than 35.31.25.," said Microsoft in a post on its Learn website.

It added that the Event Log generates an error message which reads "module is unknown" when trying to open one of the affected apps post-update. It also said that the problem is "not likely to be encountered by consumers using Windows devices in their home."

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However, Trellix Endpoint Security Agent (HX) 35.31.25 and later has now resolved the issue. Microsoft advisees that if you are still having issues, either with Trellix or other security software, then to contact their respective customer support.

Although Microsoft didn't mention it by name, Google Chrome has also been affected by the June updates, with the anti-exploit modules in security software preventing the popular web browser from opening too.

For instance, Malwarebytes confirmed that its software now mistakenly blocks Chrome since the updates. Security solutions from Cisco and WatchGuard have also blocked Chrome on Windows 11.

But while Trellix, Malwarebytes and WatchGuard have all now fixed the issue and made their respective systems compatible with the June updates, Cisco has not, with customers instead being advised to disable anti-exploit protection in the software settings or otherwise make Chrome the default browser in the Windows system settings. In the meantime, it is working on a full fix.

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Lewis Maddison is a Reviews Writer for TechRadar. He previously worked as a Staff Writer for our business section, TechRadar Pro, where he had experience with productivity-enhancing hardware, ranging from keyboards to standing desks. His area of expertise lies in computer peripherals and audio hardware, having spent over a decade exploring the murky depths of both PC building and music production. He also revels in picking up on the finest details and niggles that ultimately make a big difference to the user experience.