You can check information about each postback received from the advertiser end, through this, you can check if the postback is correctly placed on the advertiser end or not, you are getting all conversion from their end or not.
There are multiple ways you can check "Debug Postback"
1- Go to "Advertiser" > Click on Postback "Hits Received"
2- If You want to check the "Debug Postback" option for any specific advertiser then you can follow these steps-
Go to "Advertiser" > Click on "Manage" > Go to the specific "Advertiser" > Click on "Debug Postback"
3- You can also follow these steps-
Go to your Profile--- Click on "Debug Postback"