The APM 12.6 installation is by default going to use the port 1433.
In SQL server, the default instance has a listener which listens on the fixed port which is TCP port 1433.
However for the named instance, the port on which the SQL server listens is random and is dynamically selected when the named instance of the SQL server starts. This is the default behavior when the ports are not defined for the named instance manually.
When installing APM 12.6 and using SQL Server named instances with dynamic ports, the following steps must be followed to resolve the CASM installation problem, follow the below steps.
The CASM install should complete successfully.
Release: UAPMAC990JPP-12.6-Asset Portfolio Management-Asset Configuration