IMNPTF filter driver is not installed.
From WFilter Documents and Tutorials
1 Reason
IMNPTF filter driver is not installed. In pass-through mode, the IMNPTF driver is required to block udp traffic. Without this driver, some udp applications can not be blocked.
2 Solution
- Install driver in the "drivers" directory of WFilter.
- Please check: How to install WFilter IMNPTF driver?