A Reddit Post says that you actually need to use trebuchets instead. Seems there was a patch made that changed this, but forgot to update the description:
Eureka was updated in the last patch to be triggered with Trebuchets and not Bombards, but the description was not updated. Same with Replaceable Parts now needing Line Infantry and not Musketmen.
The same Reddit post references a Civilization forum post that leads to some patch notes discussion:
So as @hhhhhh posted, the tech boost trigger was changed to Trebuchets, but the text has not been updated - @Andrew Johnson [FXS]
A Firaxis member says the request was noted, but perhaps they have yet to still fix the description.
Thus, perhaps try trebuchets instead?