Valve announced another wave of troubles regarding the organisation of The International 10, which is the reason why you still can't get any tickets.
Dota 2 fans are anxious to witness another The International since it's close to two years now since TI9 happened. We all know the reason for the long pause by now and Valve are doing their best to get the show on the road again but they do seem to have rotten luck with the event.
First, they couldn't get the venue that was originally agreed on and now there are problems with selling the tickets to the fans. Technically, there isn't a brand new problem that is preventing Valve from selling the tickets. They posted an update on the issue, stating the emergence of the Delta variant of Covid-19 has been an added challenge in hosting a live event while keeping the safety precautions up.
While it doesn't offer much information on when to expect the ticket sales to go live, the update for the fans confirmed that the tournament will go on as planned. Group Stage will be running from October 7 to 10 while the Main Stage will start on October 12 and the Grand Finals will happen on October 17, 2021.
The bottom line is that the virus still sucks and Valve can't firmly promise when the ticket sales will start.