I'm glad that you were able to configure your Azure pipeline to install our @infragistics/igniteui-angular package.

The error indicates that the npm is still not configured and when installing our package, npm still searches it under the npmjs.org repo(GET https://registry.npmjs.org/@infragistics….). You can check the .npmrc file after the configuration steps by outputting it with npm list command. You can try to update the .npmrc file by redirecting the output with "TEXT" >> ~/.npmrc.
Another thing is to check whether you have a local .npmrc file per your project, which "shadows" the global one which has been updated with above steps. 

Looking at the error that you are getting, it seems that you are missing the configuration for our private repository. We have an article which you can refer to for more details how to setup your Azure DevOps build – https://www.infragistics.com/products/ignite-ui-angular/angular/components/general/ignite-ui-licensing#azure-pipelines-configuration.

Please let me know whether I can assists you with anything else on the matter.

Hello,

Can you please login to our ProGet site, and check whether do you see iginteui-angular package under the js-licensed feed here.
Looking forward to hearing from you.