Resolving SharePoint Application Authentication Error: Login Failed

Check event viewer log

• Click Start, click Run, type eventvwr, and then click OK.
• Click on Security under Windows Log

Do the following steps to resolve this error by modifying the server’s registry to specify the host name. To specify the host names that are mapped to the loopback address and that can connect to Web sites on your computer, follow these steps:

• Click Start, click Run, type regedit, and then click OK.
• In the Registry Editor, locate and then click the following registry key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\MSV1_0.
• Right-click MSV1_0, point to New, and then click Multi-String Value.
• Type BackConnectionHostNames, and then press ENTER.
• Right-click BackConnectionHostNames, and then click Modify.
• In the Value data box, type the host name or the host names for the sites that are on the local computer, and then click              OK.
• Exit Registry Editor, and then restart the computer.

The name placeholder is considered a host header. It is an alternative name for the computer on which Reporting Services is installed. You must add the NetBIOS and the Fully Qualified Domain Name (FQDN) for name to the BackConnectionHostNames list that is stored in the Windows registry.

For example, if the name is a Windows computer name, such as contoso, the name can likely also be referenced in FQDN form as contoso.domain.com. You must add both representations to the list in BackConnectionHostNames.

So, The above registry modification must be done for all other SharePoint applications which are using Host Header.