Yes.. Very unfortunately to realize that coinbase was having problems the same day that they listed bitcoin cash + the same day that they pumped bitcoin cash + the same day that GDAX was down for a whole hour because of freezing bitcoin price + the same day that the network got 280k of unconfirmed tx's.
Coinbase is the same as GDAX, so it is impossible to trade in there if the website is down, that is a simple knowledge.
A good alternative to GDAX is obviously Bitstamp or Binance, i would suggest you to use binance because you have a lot of altcoins to trade in there, and it works fine, it is not bugged all the time just like gdax is.
So yesterday morning(GMT-8, West Coast USA)) when prices were dumping and jumping, the coinbase platform which I currently use froze and halted and trades were impossible to make.