I got an email from the exchange I use stating the Istanbul hard fork is to occur at block 9069000 at approximately 15:44:36 PST on December 7. It happened already but they have suspended all deposits and withdrawals from happening until further notice.
It is not a contentious fork and so does not result in any new coins from it happening.
So why would they decide to suspend all transactions of ethereum?
Maybe it's because they're having a hard fork. Because the hard fork is one of Ethereum's own organizations and wants to set up to do another mission. sometimes they get mixed opinions and don't get support so they need to postpone it for a long time to correct things. when stable, they continue to implement their hard fork. in fact we should be happy about this, which means they are trying to improve and don't want the hard fork event to go wrong.