3222388 - How to check the correct user for setup between SAC tenant and Cloud Connector?

As you know, you can't access BTP Cockpit of SAC subaccount because it is managed by SAP. But you can set communication user in SAC UI to connect to SAC subaccount, and use this user to establish connection between Cloud Connector and SAC.
However you encounter following symptoms:

• Symptom 1:
  You added SAC subaccount to Cloud Connector A successfully several day ago, but failed to add same subaccount to Cloud Connector B even using exact same communication User ID and Password today. (Location ID has been specified)
  
  
• Symptom 2:
  You failed to update SAC subaccount certificate, even you are quite sure this User ID and Password were used to add this subaccount before.

・SAP Cloud Connector
・SAP Analytics Cloud (Enterprise) 

update, subaccount certificate, Cloud Connector, password, user, SAC, UI, create, subaccount, 1 year, communication user, SAC subaccount, , KBA , LOD-ANA-ADM , SAC Administration , BC-MID-SCC , SAP Cloud Connector On-Demand/On-Premise Connectivity , Problem