You already knew how to make your browser accept your development certificates. But today it stopped playing nicely with your Angular app again. After some trial and error you read the fine-print: Your certificate is expired! 😱
You need a new certificate to get unstuck: Delete the file server.pem in the folder node_modules\webpack-dev-server\ssl
Next time you start up your development server (ng serve –ssl true) a new certifcate will be generated and life is good again. Don’t forget to add the new certificate to the certificate store.