ionic-cli: Unable to find command - ionic serve after upgrade to 4.0.2 from 3.20.0

Description: I just upgraded Ionic Cli from 3.20.0 to 4.0.2 and tried to run ionic serve and it shows error Unable to find command.

ionic info also does not work.

Please check image.

About this issue

I believe the solution is to uninstall fully and then re-install:

npm uninstall -g ionic
npm install -g ionic

+13

@dwieeb after switching to npm registry, the installation goes well. thanks