2 Days ago management of .io registry was transfered from Afilias to Donuts (Due to an acquisition). It is likely that during that window you registered the domain and they are now cleaning up the issue. It may be your registrar took your registration and then when they went to actually process it the registry was down, so someone else got it during that period. It could be other things, however, the bottom line is that the domain was probably never yours and there is really not much to do here. It's bad timing and bad handling of a process on your registrars end.