ionic serve can run
ionic cordova build android (--release) and then generate platforms, but the folder is empty:

this is the way it is now. I don"t know what went wrong. It used to be fine. There was nothing wrong with it. When National Day came, it became like this.

I thought it was the version. I uninstalled the cordova8 version and reinstalled the 7 version.

$ ionic cordova build android 

> cordova platform add android --save
Using cordova-fetch for cordova-android@~6.2.2

Error: Failed to fetch platform cordova-android@~6.2.2
Probably this is either a connection problem, or platform spec is incorrect.
Check your connection and platform name/version/URL.
Error: cmd: Command failed with exit code 1 Error output:
npm ERR! code E400
npm ERR! 400 Bad Request: cordova-android@~6.2.2

npm ERR! A complete log of this run can be found in:
npm ERR!     C:\Program Files\nodejs\node_cache\_logs\2018-10-08T07_14_12_885Z-debug.log

[ERROR] Exception:

still no,