Why was my first online 90-day report rejected after reentering Thailand?

In the body of the email that is headered like this

[𝗧𝗠.𝟰𝟳] (𝗣𝗔𝗦𝗦𝗣𝗢𝗥𝗧 𝗡𝗢 : *********) 𝗙𝗢𝗥𝗠 𝗙𝗢𝗥 𝗔𝗟𝗜𝗘𝗡 𝗧𝗢 𝗡𝗢𝗧𝗜𝗙𝗬 𝗢𝗙 𝗦𝗧𝗔𝗬𝗜𝗡𝗚 𝗟𝗢𝗡𝗚𝗘𝗥 𝗧𝗛𝗔𝗡 𝟵𝟬 𝗗𝗔𝗬𝗦 𝗛𝗔𝗦 𝗕𝗘𝗘𝗡 𝗥𝗘𝗝𝗘𝗖𝗧𝗘𝗗

It usually says the reason for your rejection (although sometimes it doesn't)

The reason you were denied is that since the system was upgraded (a few months back) the FIRST time you report after coming back into the country you have to do it in person.

Many people have been denied their initial 90 day report after coming back into the country.

You can certainly try again (as you're well within the window 2 weeks before down to 1 week before)

BUT

as I said, it's not uncommon to be denied online when you try the first report after coming back into the country