Ducati Multistrada 950S 2019 Owner's Manual page 312

Closing
Close the side pannier as follows.
Lift and close the external cover by engaging the
edge in the relevant channel on pannier fixed part:
A
bag will close only in these conditions.
Insert fastening plate (A) into the pannier external
cover and push down.
Turn key counter clockwise.
It is possible to remove key from lock only in these
conditions.
Fig 273
311