Here's a novelty. I tried to do my 90 day report online and after an approval last time, this time it came back Rejected. Nothing had changed, all paperwork in order. A message from the IO said to contact the office where my visa was issued. That was the Thai embassy in London, so I don't think they could have helped me.
So, I went to do the report in person at Hua Hin. They were their usual efficient and friendly selves and I made my report with no problems. I asked the IO why my online report had failed and she told me that only around 2 online reports in the Hua Hin office region are approved per day. She said that for other offices, the figure is higher, maybe 100 per day. She did not know the reason why this should be. It seems strange to have a quota system like this and to reject perfectly valid online reports, the acceptance of which would greatly reduce the workload in the immigration offices.