On Oracle Applications 12.2.4 and higher , login page is not coming and  errors with HTTP 500

Port number in WebLogicCluster parameter specified in httpd.conf is not an integer less than 65535, or servers are not specified correctly. Cannot

The issue can be reproduced at will with the following steps:
1. Log into Applications.
2. Error occurs.

An incorrect NULL or wrong entry in the mod_wl_ohs.conf.

1. Please compare following files with a working instance:

Especially for section:

  SetHandler weblogic-handler
  WLCookieName JsessionIDOAFM
  WebLogicCluster null
 2. Change the WebLogicCluster to the correct value and re-test.