Ok, first, some terminology. One, you are showing the system for 90-day reporting. This is NOT the same as 'extending your stay'. No, I'm not being snarky. It's important to understand b/c, using simple deduction, I can tell you that you are in Thailand with permissions derived from an agreement b/w Thailand and your home country to allow you to legally enter and dwell in Thailand for a pre-determined period of time.
As you are exempt from the burden of having a visa, you do NOT need to do the 90-day reporting as shown in the picture above. The reason it keeps failing is that your passport number and/or name is coming back empty from the database of eligible people to do 90-day reporting.
The amnesty allows you to remain in Thailand worry-free, with no reporting. All they ask is that you work on an exit strategy when September 26th rolls around. If like it has done twice in the past, no strategy is available, an extension or other administrative action from the Thai government will transpire.
Again, we’re waiting on what immigration themselves have to say in regards to procedure (or lack thereof). This post was just to let everyone know SOMETHING is happening so they can breathe easier.