Cannot convert table when saving to a DataStore?

I get this error : Cannot convert mixed or non-array tables: keys must be strings on this line

datastore:SetAsync(player.UserId,data2)

Yet I have similar scripts that save similar tables which work. Any ideas? Whole code:

function save(player,data)
		local data2={
	["Bed"]=0,
	["Chest"]=0,
	["Fireplace"]=0,
	["Foundations"]=0,
	["Furniture"]=0,
	["Walls&Roof"]=0,
	["Wooden Structure"]=0	
}
	for i,v in pairs(data) do
		data2[v] = 1
	end
	local datastore = game:GetService("DataStoreService"):GetDataStore("Housing")
	datastore:SetAsync(player.UserId,data2)
end


--PLAYER LEAVES---------------
game.Players.PlayerRemoving:connect(function(player)
	
	local data= player.HasTycoon.houseBuilds:GetChildren()
	if data then
		save(player,data)
	end
end)

EDIT: as suggested this line

datastore:SetAsync(player.UserId,data2)

was updated to

datastore:SetAsync(tostring(player.UserId),data2)

but the problem persists with the same error message

The problem here is that you are trying to save a table to DataStore, which is an unsupported data type.

The only way around this is to use a "compiler" to translate the entire table into one long string. The best way to go about this is by using HTTPService and the functions JSONEncode and JSONDecode. Just before you use the SetAsync() function, add the following line:

data2=game:GetService("HTTPService"):JSONEncode(data2)

This compiles your table into an easy-to-save string. Then, when it's time to load the data, use JSONDecode() and you'll wind up with the exact same table you started with.

I hope this helped!