To test that the Thrive global post-back URL is working as it should, you can go to:
Tracking > Click/Conversion Log
Find an existing sub ID, let's say it's 12345, as an example.
Then get your post-back URL, and put the sub ID after the post-back, like so:
Then, copy and paste it into your browser URL bar to execute the post-back.
Once it's executed, you should see a blank white page.
Wait ~5 minutes, and the conversion should show up in your Click/Conversion Log in Thrive.
You can do a search for the sub ID, then filter for Conversions. If the sub ID appears in the list, then it worked as expected.
The payout amount should also be the default payout amount for that offer.
You can check the campaign associated with that sub ID, and the revenue should be increased by that amount.