There is a basic check you can perform and ensure its correct :
1. After installation the gateway setup will ask email id > Ensure the same email is added/used to login to Power BI service.
2. Ensure the Gateway is up and running.
3. Some time organization blocks the content due to which Service does not load properly. Use your non-organization laptop to login and see if the Gateway is visible or not. If Yes then its Browser if not then need to explore different angel.