How would I fix "Can't Parse JSON" in this situation?

		local tab,endtime = game.ReplicatedStorage.orders.makeLocalBooking:InvokeServer(tonumber(script.Parent:WaitForChild("num").Text), selectedguest.Name, grpbook, tonumber(script.Parent:WaitForChild("tabnum").Text))
		if tab and endtime then		
			local formattedtime = string.format("i",math.floor((endtime% 86400)/3600)+timezone)..":"..string.format("i",math.floor((endtime% 3600)/60))
			script.Parent.response.Text = "User booked onto Table "..tab.." until ".. formattedtime..  " BST."
			wait(5)
			script.Parent.grp.n.Text = "X"
			script.Parent.grp.y.Text = ""
			script.Parent.num.Text = "#Num"
			script.Parent.tabnum.Text = "#Num"
			script.Parent.guest.Text = "#Name"
		else
			script.Parent.response.Text	= "An error occurred, please try again."
		end
		deb = false
	end
end)```

How can I fix this? It comes up with "Can't parse JSON"