I can't use creative cloud on photoshop touch app on android anymore.  I really want to know why this happens.  I can log in and upload, or download files to cloud by web but I still can only see the message 'cannot connect to server'

Sometimes the sign-in process goes kablooey for whatever reason. It can usually be remedied by tapping the options icon (the cogwheel out in the project selection user interface; upper right) > My Account. Sign in that way and you should be able to get everything going again. I just did it on my Google Nexus 7 2013 with no problems.