Checking the nonProxyHost Settings for the Theme Editor 
If the Theme editor's preview function does not work correctly, you need to check that the portal is configured with the correct nonProxyHost settings.
In SAP NetWeaver Administrator, choose .
In the Module List section, select the com.sap.portal.ivs.httpservice application.
In Web Module Details, in the Components tab, select the proxy service.
In the Portal Service Details area, select the HTTP - Bypass Proxy Servers property, and enter the relevant server information. For example, *.yourCompany.
Note
Separate entries with a pipe character ( | ).
Restart the proxy service: