As per their website this is the best explanation I could find:
"Announcement: Site technical issues (click/tap here for more details)
PokerStars Sports is currently undergoing unscheduled maintenance following tech difficulties.
Features such as logins, markets, in-play betting, and betting history will be affected. We’re sorry for the inconvenience.
Rest assured we’re working on getting back up and running as soon as possible.
In the meantime, your account balance is safe. Any pending bets will be settled as soon as the maintenance is complete"