3450920 - NWA throwing 503 service unavailable error: WebApplicationException

NWA links throws 503 error.

default trace:

Error#com.sap.engine.services.deploy.server.application.ApplicationTransaction#
#BC-JAS-WEB#servlet_jsp#C0000A89A20C001F0000000100011C0C#32312950000001463##com.sap.engine.services.deploy.server.application.ApplicationTransaction#64E4C59AEBD811EE95F9000001ED0E76#64e4c59aebd811ee95f9000001ed0e76##0#Deploy Start Application Thread(76)#Plain##
Error in starting application [sap.com/tc~wd~dispwda].
[EXCEPTION]
com.sap.engine.services.servlets_jsp.server.exceptions.WebDeploymentException: Error in starting application [sap.com/tc~wd~dispwda].
   
Caused by: com.sap.engine.services.servlets_jsp.server.exceptions.WebDeploymentException: Error occurred when invoking start methods of web container extensions for [sap.com/tc~wd~dispwda] application.
    
Caused by: com.sap.engine.services.servlets_jsp.server.exceptions.WebDeploymentException: Error occurred when invoking start methods of web container extensions for [sap.com/tc~wd~dispwda] application.
    
Caused by: com.sap.engine.services.servlets_jsp.server.deploy.impl.exceptions.WCEDeploymentException: Operation [prepareStart] for [webdynpro/resources/sap.com/tc~wd~dispwda] web application is not possible because required Web Container Extension provider [GPAL] is not available. Possible reason: Web Container Extension provider has taken part into deployment process, but now is not available.
  

NW AS Java 7.50

GPAL,AS Java, tc~pp~gpal~deploylistener, nwa, 503 service unavailable , KBA , BC-JAS-COR , Enterprise Runtime, Core J2EE Framework , Problem