I open the “}APQ UX Notification User” dimension, there are not such users. But I can’t edit the dimension to add both of them. Please advice how to proceed. Thanks.
The UX Content Store uses alternate hierarchies which are not visible in Architect. You should not under any circumstances ever attempt to edit anything in the Content Store using Architect. IT is a surefire way to break your content store. For that matter you should only ever edit the content store manually using an IDE which does support hierarchies (such as Arc) if you know exactly what you are doing.
It appears that you are an Apliqo FPM customer. Apliqo FPM uses a customized version of Apliqo UX which has its own installer. You should never upgrade a Apliqo FPM application with the standard Apliqo UX version as this could cause FPM features to break.
At this point it would be helpful to know which customer site you are associated with so that the appropriate person from the FPM team can help you directly.