Hi Hridyesh,
Don't know the history of your server, or what has been done prior the change.
If you have verified the admin ui before this integration or not.
There is no reason to think somehow Identity minder 12.5 integration broken admin UI.
Although I highly recommend customer to check with IDM support to be sure they are installing the compatible versions of IDM and Siteminder.
However, the message itself does indicate you have a corrupted installation of admin UI. The content probably is not properly deployed onto JBoss.
We can find a number of cases with exact same error message. In all those cases the solution was to uninstall and re-install the adminUI. Make sure you follow the Siteminder documentation of your version on installing admin ui pre-req and admin ui.
Hongxu