Paypal standard not working

im having many problens whit paypal on my ecommerce
im using opencart 2.0.3.1 and when some customer make any order whit paypal payment it isnt showed on order list
in db, status id is always 0 even in sucess payment
im using paypal standard and i configured the return url and NIT return information on my paypal account.
could some one help me please?
i tryed to make every thing that i saw on google to fix that

Are the orders actually being processed? Does it return the customer to the success page after payment?

-Tim