2996470 - The chosen operation is not currently available NWDS 7.5

By right click on a project in the Enterprise Portal perspective and select option 'Add Class to Build Path'

and get error 'The chosen operation is not currently available.'

The .log file in the metadata directory under the NWDS workspace could contain errors like these:

!ENTRY org.eclipse.ui 4 4 2020-12-01 08:20:42.505
!MESSAGE Could not create action delegate for id: IJavaProjectAcion
!SUBENTRY 1 org.eclipse.equinox.registry 4 1 2020-12-01 08:20:42.505
!MESSAGE Plug-in com.sap.ep.classlocator was unable to load class com.sap.ep.classlocator.actions.OpenLocateClassWizardAction.
!STACK 0
java.lang.ClassNotFoundException: An error occurred while automatically activating bundle com.sap.ep.classlocator (1118).

Caused by: org.osgi.framework.BundleException: Error loading bundle activator.
at org.eclipse.osgi.internal.framework.BundleContextImpl.start(BundleContextImpl.java:721)
at org.eclipse.osgi.internal.framework.EquinoxBundle.startWorker0(EquinoxBundle.java:933)
at org.eclipse.osgi.internal.framework.EquinoxBundle$EquinoxModule.startWorker(EquinoxBundle.java:309)
at org.eclipse.osgi.container.Module.doStart(Module.java:581)
at org.eclipse.osgi.container.Module.start(Module.java:449)
at org.eclipse.osgi.framework.util.SecureAction.start(SecureAction.java:468)
at org.eclipse.osgi.internal.hooks.EclipseLazyStarter.postFindLocalClass(EclipseLazyStarter.java:103)
... 46 more
Caused by: java.lang.ClassNotFoundException: org.eclipse.core.internal.compatibility.PluginActivator cannot be found by com.sap.ep.classlocator_1.0.0

SAP NetWeaver Developer Studio 7.5

KBA , BC-DWB-JAV-COR , Core Frameworks , Problem