However, i think i may have a idea why.
I always check Matomy Videos first as they always have some, But i noticed that when some of the videos load in the load bar at the bottom of my screen it looks as if they are pulling in the video from V11 Media (which i gather is V11 Media Videos). And normally all the videos that appear in V11 are always in Matomy Videos.
If this is the case then clearly they wouldn't want to pay you twice.
This is just a hunch based on what i have seen ect and may not be the reason for them not crediting but sounds more likely that it could be.