As I understand it, the Validation Test was REQUIRED for the rebate. The people that are not getting the rebate will get validated as they fly.

I am one of the lucky people that just installed ADS-B out and was required to do a validation test. AC20-165B has the requirements of what the FAA wants to see. My first validation test flight (after I had my 91.411 / 91.413 tests completed by a local avionics shop) actually failed because I only was 26-minutes in rule airspace. I miss read the requirements and flew part of the flight outside the mode C veil. The email from the FAA said they would manually validate and get back to me in 3-days. One week later, I had heard nothing so re-flew the test this time with over 1-hour in the mode C veil but part of the maneuvers were outside it. The Rebate Validation flight link failed to generate a report. I went to the public report generation sight and was able to get a report. I took the end time of the public report subtracted 15-minutes and then want back to the rebate validation website and use the time I just derived to request a report. The report came back all GREEN so I passed and there was a Rebate Request CODE to enter on the website. They say the rebate check will arrive in 4-weeks. One of my friends just got their rebate check after 8-weeks.

IF you are going ADS-B out by way of a Mode S transponder, you can see some of the info that the FAA is seeing by going to FlightRadar24.com and entering the number of the aircraft. One can see data up to 7-days old without paying a subscription fee.