I upgraded EEM to 12.6.3 and SOI to CU4.
SOI console opens with no "Alert Queues" tab. I have tried multiple times including clear cache and close out all other apps, but the problem still persists.
Release : 4.2 CU4
Component : Service Operations Insight (SOI) Console
The issue has been resolved after updating the JRE from Version 1.8 update 301 to update 341c.
In some cases, an error on the customization of the Label of UserAttribute4 could cause the whole Alerts tab to disappear.