They are not in Artillery foundry anymore and I saw in notes there is something special about French and their grenadiers but I can not figure out what is needed to create them.
They are linked to the Church card now.
Send the edict of Nantes card and a tech sending Grenadiers will appear in your church. This will also enable Grenadiers in your artillery foundry.
You can research the tech two more times, improving the send grenadiers and upgrading all your grenadiers with the arsenal tech on the second research and grenade launchers on the third.