You need to see what port offset you are using in your JVMs/servers. Eg: if it is +100 then it means you need to access webapp URL as http://localhost:8180/webapp
Can you send screenshot of management console with server instances please? or send the server.log of respective log file?
I guess may be you are using a wrong port # to access webapp.
Go to $EAP_HOME/domain/servers/<server-name>/log/server.log
Search for 127.0.0.1 or localhost in server logs.
You will get the port # from server logs.
Try accessing webapp via that port #