I open the browser and open the "arcgis.com" home page(www.arcgis.com/home). When I click the button "Sign in", It could not work. I wait for more than 10 minutes, try to change a different browser, clear the record and do anything I can. However it still dosen' work. I have used this computer to log in for a few times. Then I try to use it again. This problem occured. It happen very often.
I hope that you can figure out the reason and help me. Thanks a lot.