Symptoms
Consider the following scenario:
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Microsoft Exchange Server 2016 Cumulative Update 7 (CU7) is installed on a computer that's running Windows Server 2016.
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A user signs in Outlook on the web (Outlook Web App) and tries to change the language through:OWA > Options > General > Region and time zone settings.
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The user selects the language that has an LCID value of 4096, for example, English Belgium.
In this scenario, the user receives a "something went wrong" error message and OWA crashes. This issue prevents the user signing in until the administrator changes the language setting back to a supported one. In addition, you may find the following event logs are recorded:
Exception type: System.Globalization.CultureNotFound Exception Exception message: Culture isn't supported. Parameter name: culture 4096 (0x1000) is an invalid culture identifier.
Cause
This issue occurs because the newly-added cultures don't have valid LCIDs.
Resolution
For Exchange Server 2016, install Cumulative Update 9 or a later cumulative update for Exchange Server 2016.
Status
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
References
Learn about the terminology that Microsoft uses to describe software updates.
