The required steps differ depending on the product or app you use.
If you have communication restrictions in place, please configure the necessary permissions and settings in advance, and then verify the connection using the actual device, app, and network you intend to use.
Web Browser version, Mobile Browser, and Mobile App
No per-app configuration is required.
Please configure the proxy settings on the device or Browser you are using, and also verify that the proxy server is configured to allow connections to the Teachme Series.
Related: What URLs and ports need to be allowed for communication in order to access the Teachme Series?
https://help.series.teachme.jp/hc/en-us/articles/63062069456025