Hi, and sorry about the issue! The course is working, so please try the following
- Use Chrome. Make sure it's up-to-date, and is the stable channel.
- Add a new Chrome person. Go to the Add a person or profile section and follow that.
- Under that new person, try things out again.
This ensures more than trying other browsers or using incognito that 1) there are no extensions 2) and it also makes sure the settings are default, so for example 3rd-party cookies aren't blocked, plus no experimental features are enabled.
If that doesn't work, please check for any firewalls or similar proxies that are interfering. These may be on your computer, or on your network. For example, work places often have a firewall or similar proxy installed, and wifi routers, too, can modify packet headers and interfere with with web sites.