Went to pick up my passport today. Asked from the lady at the counter if she knew why online reporting failed as been working Ok before. She took my passport and looked the stamps and said 'first time, after this online ok'.
Seems indeed that how need to report first one after arriving the country in person and online Ok after that. Or possibly first one after extension of stay renewal, pity that came to my mind just after leaving.
I was trying to figure out the logic of why first time in person but after that can do online. Only explanation credible to myself was that there must have been two camps in immigration, one insisting online Ok always, and the other camp of the opinion that no online should exist at all. Then these groups make a political compromise in some obscure committee meeting that first time in person and after that can online.
TIT.