there is a maintenance page if you try to access Bitsler
there are parallel DDOS attacks going on as we  speak,many top crypto casinos are affected
my guess would be that the attack is too strong at the moment and admins decided to close the site for maintenance
far too many ... individuals nowadays who think that once they discover a DDOS site,they could invest 500$ and try to blackmail casinos for coins
pretty sure one of the admins will come online soon and provide more info