IPN return Invalid

[PenguinArts]

I am trying from yesterday to implement the IPN but it return INVALID all the time. Today I found this repo but it return invalid too.

This return in the OnInvalid function:
INVALID

payment_type=instant&payment_date=Thu+Jun+14+2018+00%3A50%3A21+GMT%2B0300+%28GTB+Daylight+Time%29&payment_status=Completed&address_status=confirmed&payer_status=verified&first_name=John&last_name=Smith&payer_email=buyer%40paypalsandbox.com&payer_id=TESTBUYERID01&address_name=John+Smith&address_country=United+States&address_country_code=US&address_zip=95131&address_state=CA&address_city=San+Jose&address_street=123+any+street&business=seller%40paypalsandbox.com&receiver_email=seller%40paypalsandbox.com&receiver_id=seller%40paypalsandbox.com&residence_country=US&item_name1=something&item_number1=AK-1234&tax=2.02&mc_currency=USD&mc_fee=0.44&mc_gross=12.34&mc_gross_1=12.34&mc_handling=2.06&mc_handling1=1.67&mc_shipping=3.02&mc_shipping1=1.02&txn_type=cart&txn_id=910839206&notify_version=2.1&custom=xyz123&invoice=abc1234&test_ipn=1&verify_sign=undefined

In IPN Simulator when I try to send a test I got this error: IPN was not sent, and the handshake was not verified. Review your information.

[PenguinArts]

I have just solved it. I will let this here if anybody will have this problem. https://stackoverflow.com/questions/32586711/ipn-was-not-sent-and-the-handshake-was-not-verified-please-review-your-informa?utm_medium=organic&utm_source=google_rich_qa&utm_campaign=google_rich_qa

There is a problem with IPN Simulator that's why it return all the time INVALID. Your code probably works good like mine too, but Paypal has problems with their dev teams I guess.