Please help! Why my driver gets unloaded before DriverEntry on Longhorn

I am trying to test my FSD driver on Longhorn (build 5384).
The driver gets unloaded and I cannot break into debugger in DriverEntry.
(I am calling DbgBreakPoint in DriverEntry)

kd>lm t n

Unloaded modules:

8da48000 8dc00000 mydriver.sys
Timestamp: unavailable (00000000)
Checksum: 00000000

88de6000 88e00000 serial.sys
Timestamp: unavailable (00000000)
Checksum: 00000000

Does anyone have any idea?
-Jeff