Not able to open a Data Protocol Handler in the VSM Listen step under Filters.
When selecting a DPH filter, nothing happens.
It is possible that a new jar file was added to $LISA_HOME/lib folder and is not playing well with DevTest, causing the issue.
When looking at the Workstation log files, exceptions like ClassNotFound were being generated and referring to an external jar file.
Removing the additional jar file from $LISA_HOME/lib folder and restarting the Workstation resolves the issue.
The custom extension needs to be reviewed.