Bittrex, one of the largest US cryptocurrecny exchange, had suspended new users registration almost 5 months ago "due to a large spike in new user sign ups".
On April 11, it tried to resume it, but due to technical issues, users were able to register only for one hour. At the same time, Bittrex introduced an updated design of its site and trading platform and also increased security level, as company notes.
Recently, Bittrex reported on the registration issue fix.
Registration is working properly for 16 hours, so we hope that there won't be any issues. Bittrex is popular with fans of altcoins. It has around 180 coins listed.