Ionic resources returns 410 (gone) error?

“ionic config set backend pro -g” not worked for me, has someone got this problem? how to solve it? Thanks in advance.
my ionic info:

@ionic/cli-utils  : 1.19.2
ionic (Ionic CLI) : 3.20.0

global packages:

cordova (Cordova CLI) : 7.0.1
Gulp CLI              : CLI version 3.9.1 Local version 3.9.1

local packages:

Cordova Platforms : android 6.2.3
Ionic Framework   : ionic1 1.0.0-rc.4

System:

Node : v6.10.2
npm  : 3.10.10
OS   : Windows 10

Environment Variables:

ANDROID_HOME : not set

Misc:

backend : legacy