I think it is because it has no indication to which archeology site it belongs.
What can I input into the {} of the command line
/give [playername] betterarcheology:fossiliferous_dirt{}

Jep, that is correct. The mod uses processor_lists to assign the right LootTable at runtime.
That way I don't have to redo all the structures when I want to change the LootTables.

I am unsure if it is possible to do that with /give since that data is written into the BlockEntity but here's a template for a /setblock command:

/setblock x y z betterarcheology:fossiliferous_dirt{LootTable:"location"}

For location, you can use every sort of loot_table. BetterArcheology has these paths, if you want to use the built-in ones:

betterarcheology:archeology/fossiliferous_dirt_chicken

betterarcheology:archeology/fossiliferous_dirt_creeper

betterarcheology:archeology/fossiliferous_dirt_jungle

betterarcheology:archeology/fossiliferous_dirt_sheep

betterarcheology:archeology/fossiliferous_dirt_villager

betterarcheology:archeology/fossiliferous_dirt_wolf

betterarcheology:archeology/fossiliferous_dirt_guardian

betterarcheology:archeology/desert_sand

betterarcheology:archeology/plains_gravel

betterarcheology:archeology/taiga_dirt

betterarcheology:archeology/mesa_red_sand

Thanks that was very helpful.
The /give command seem not to work but the /place command works perfectly fine.