In SDL Tridion, missing msxml4.dll file causes invalid license error while logging in to CMS

While logging into CME content editors see error"Unable to get object: LicenseInfo Invalid license Unknown Error" System.ServiceModel.FaultException`1[Tridion.ContentManager.CoreService.Client.CoreServiceFault]: Unable to get object: LicenseInfo Invalid license Unknown Error (Fault Detail is equal to Tridion.ContentManager.CoreService.Client.CoreServiceFault). 

- If inspecting the license.xml file in %TRIDION_HOME%/bin directory, license file does not have an expiration date or expiration date is in the future.
- In the Windows event viewer, Tridion and Application categories, the below events can be seen

Unable to get object: LicenseInfo
Invalid license
Unknown Error
Component: Tridion.ContentManager.Publishing
Errorcode: 3
User: NT AUTHORITY\SYSTEM
StackTrace Information Details:
   at Tridion.ContentManager.Licensing.LicenseInfoClass.Initialize(String ProductName, EnumLicenseLockTypes LockType, Object& cookie, String licenseConfiguration)
   at Tridion.Licensing.LicenseInfo..ctor(String productName, LicenseLockType lockType, String licenseFileName)
   at Tridion.Licensing.LicenseInfo..ctor(String productName, LicenseLockType lockType, String licenseFileName)
   at Tridion.Licensing.LicenseManager.GetLicenseInfo(String productName, LicenseLockType lockType)
   at Tridion.Licensing.LicenseManager.GetLicenseInfo(String productName, LicenseLockType lockType)
   at Tridion.ContentManager.LicenseHelper.StartupLicenseCheck(Session session)
   at Tridion.ContentManager.Session..ctor()
   at Tridion.ContentManager.Publishing.Publisher.DeploymentFeedbackHandler.DoWork()

Check if msxml4.dll is present and add the file again if it is missing.  On a Tridion 2013 SP1 HR1 server, this could be verified with following steps:
- msxml4.dll is installed to C:Windows\sysWOW64 folder.
- MSXML 4.0 SP3 Parser is listed under Add/Remove Programs

- MSXML4 is required on the CME and Publisher servers only, not the CD servers (such as Deployer server).

If msxml4.dll needs to be installed and the original dll is no longer available, it can be downloaded from below Microsoft link.  It had originally been installed as part of the Content Manager installer.
https://www.microsoft.com/en-us/download/details.aspx?id=15697
The installation documentation link may also be helpful
https://docs.sdl.com/LiveContent/content/en-US/SDL%20Tridion%20full%20documentation-v1/GUID-A6CBE401-9EB7-4534-9362-4B15B19B290E
 

This issue can be caused by the msxml4.dll being removed from the system.

Note that in SDL Web 8.5, MS XML 6.0 can be used.  MSXML 4.0 is only required when using legacy components.

Also see KB article When attempting to startup SDL Tridion, this fails with error "Automation error The specified module could not be found"