Documents aren't displayed in web browser when you're using TLS 1.2
When you use web apps in Microsoft Office Online Server, documents are not displayed in the web browser as expected. Instead, you receive an error message that resembles the following:
We're sorry, we ran into a problem completing your request...
Additionally, you learn that TLS 1.0 has been disabled on the SharePoint web front end servers through the registry entry that's provided in the following Microsoft Knowledge Base article:
TLS 1.2 is not currently supported because Office Online Server (and Office Web Apps) uses .NET Framework 4.x to establish network connections. By default, .NET Framework 4.x doesn’t support TLS 1.2.
Microsoft released the following optional security update to .NET Framework 4.x, which changes the default encryption protocols:
This update changes the default encryption protocols from SSL 3.0 or TLS 1.0 to the following: TLS 1.0 or TLS 1.1 or TLS 1.2
Note This security update won’t be released for Windows Server 2016 or later. Starting with Windows 2016, the registry keys that the optional security update automatically sets will have to be manually configured on each Office Online Server computer. Those registry keys and settings are as follows:
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramework\v4.0.30319] "SchUseStrongCrypto"=dword:00000001 [HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432N ode\Microsoft\.NETFramework\v4.0.30319] "SchUseStrongCrypto"=dword:00000001