Hi R-jay
Not sure if you are on single stack or dual stack. Anyway, here is the UDMS setting for SFTP on my single stack system that works.
For the search criteria, I use the following namespace (which also is the same namespace in my sender SFTP channel)
http://sap.com/xi/XI/SFTP/SFTP
Here are the results when searching using UDMS in the message monitor. I enter value *.txt and find a message that fulfills that criteria.
Rgds
Eng Swee