Last year there were over 250 000 active participants and it's set to go up again this year. We're talking about a site that has next to no traffic for 11 months then over 100 000 people trying to do stuff. Plus the early bird team selection opened earlier today (which is a couple of days late compared to previous years) so the servers are way oversaturated at the moment, and most likely will be until at least the 3rd of July.
You can still use the site but it's very laggy.