I don't know whether someone has posted this or not, so ignore this if it is old news. The infrastructure at Bittrex wasn't capable of handling the rapid scaling of an onslaught of new users and had to shut down new account registrations (until further notice). My guess is that a lot of the exchanges are likely in the same boat.
New Account Sign Ups
December 15, 2017 10:21
Dear new users:
We have received an enormous number of new account registrations over the past few weeks. We are excited to have so many new users who want to join the Bittrex community. Unfortunately, we have to make a few upgrades to our support and backend systems to handle the increased traffic and load. As such, we have halted new user registrations for the time being. If you already have an account on Bittrex, you will not be affected by this change. Please continue to the log in as you normally do.
To our new users, we will keep you posted on when we open up registration. We apologize for the inconvenience!
The Bittrex Teamhttps://support.bittrex.com/hc/en-us/articles/115003463331It is very demanding and costly to build a top notch exchange. We are committed to build our own and do it right. It will cost $ millions and may take a little longer. But that is a vital component of our fully integrated system. If I have my way, we will have the best customer services - something annoyingly lacking in our industry.