How to Troubleshoot Sage CRM Tomcat issues. HTTP 404 error

Start with testing page http://localhost/sdata/ j/sagecrm/-/$schema to see if an XML page is loaded. (Try to use Chrome as IE display XML as blank page)
If HTTP 404 error, then follow these steps to determine which area causing issue :

1. Apache Tomcat service not running
   Try to restart Apache Tomcat service from Start, Administrative tools, Services. Wait for one minutes and check if CRM interactive dashboard loads.
2. Java related issue(7.1 version or prior)
   CRM 7.0 and CRM 7.1 requires Java 6 runtime environment. Please remove all the installed Java version in Start, Control Panel, Programs and Features. Download and install Windows x86 Offline version from http://www.oracle.com/technetwork/java/javase/downloads/jre6downloads-1902815.html
   CRM 7.2 or later provides its own Java 7 runtime so the Java version in Windows is not an factor.
3. Redirect related issue
   CRM7.0: check if IIS Manager, default Web Site, ISAPI filters shows CRMUrlRewriter and CRMUrlRedirector
   CRM7.1: check if ASP and ASP.NET are installed in Start, Administrative tools, Server manger, Roles, Web Server (IIS), Add Roles Services, under Application development, enable ASP.NET, .NET Extensibility, ASP, ISAPI Filter, ISAPI Extensions and Server Side Includes.
   
   CRM7.2 or later:
   1. 1. Check if URL Rewrite are in IIS manager, Default Web Site, Sdata. URL Rewrite only supports in Windows server 2008 or newer operating system.
      2. Open URL Rewrite module , double click each Inbound Rules and replace {C:1} with localhost for all the URL rewrite rules.
         ie http://{C:1}:10009/crmj/{R:1} change into http://localhost:10009/crmj/{R:1}
      3. Check Action URL Port matching the tomcat port in Server.xml
         
                          
4. CRMRewriter App Pool configuration issue
   In IIS Manager, Application Pools, CRMRewriter App Pool, Advanced Settings. Make sure .NET Framework Version is set to V4.0, Enable 32-Bit Applications set to True and Managed Pipeline Mode is set to Integrated.
5. Anti-virus and Windows firewall
   Sometimes a tight security can block the Tomcat port, which is by default set to 10009, 11009 or 12009. Disable Windows firewall to see if that causes issue. To disable it, go to Start, Control Panel, Windows Firewall, Turn Windows Firewall on or off and click on Turn off Windows Firewall. To turn off Anti-virus program, please consult its provider.
6. Database connection parameter not set correctly.
   Open db.properties (formerly jdbc.properties) in CRM installed directory with Notepad, it is located in ..\CRM\ \tomcat\webapps\ j\WEB-INF folder. Make sure the SQL server name, port, any instance name, SQL user name and password are all correct.
   
   Below is the code section on Tomcat's db.properties file, if no database instance needed then take out the "instance=" part:
   
   db.url=jdbc:log4jdbc:jtds:sqlserver://[ServerName]:[DBPort]/[CRMInstance];language=English;instance=[DBInstance]
   db.username=[DB Username]
   db.password=&NDEFPBJKIOKFEMPFKCOIGLIGABLPBDNF
   
   Please note db.password is encrypted & obtain from registry, copy it from HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\eWare\Config\/[instance] > DatabasePassword.
   Tomcat can't interpret password prior to encryption with special characters in the beginning and at the end (ie. !Password%)
7. Tomcat program not installed properly:
   To reinstall Tomcat :
   1. Stop Apache Tomcat Service in Windows Services
       2. Delete entire folder "tomcat" in C:\Program Files (x86)\Sage\CRM\[CRMInstance]\
       3. Run Sage CRM setup.exe, select Install SageCRM, Next, accept user license,
   Change existing install of CRM, select existing CRM install name,
   select only Program files and IIS Aliases to continue installation.