Unable to login to AWI after ZDU | The credentials are not valid

Products

• CA Automic Operations Manager

Issue/Introduction

While using ZDU to upgrade within 12.2, unable to log into the new, upgraded AWI on tomcat and seeing the error:

com.uc4.ecc.backends.exceptions.AutomationEngineAPIException: [HTTP 401] (45107) Cannot logon to Automation Engine.: The credentials are not valid.

The PWP logs show:
PWP shows: 20210512/213220.320 - U00003205 Logon of 'System UC4' ('UC/UC'), client: '0000' accepted by host '[server_name]'. Client version = '12.2.7+build.1600710879953', type='Java-API' (connection='*CP003#00000034').
20210512/213222.610 - U00011852 Logoff 'System UC4' ('UC/UC'), client: '0000' (Connection='*CP003#00000034').

The JCP logs show:
20210512/213222.563 - 61 U00045098 Method 'GET', URL: 'http://[AUTOMIC_SERVER_FQDN]:12281/ae/api/v1/0/system/features', received from IP: '<IP Address>'
20210512/213222.579 - 61 U00045099 The server replied with following status: '401'

Environment

Release : 12.2

Component : ANALYTICS ON PREMISE

Resolution

1) backup the config files from the new awi /config directory
2) remove the new awi .war file
3) Wait for the new awi folder to disappear from tomcat's /webapps directory
4) put the new .war file back into the /webapps directory
5) put the config files from step 1 back into the new awi /config directory 

Then logging in should be possible