If you are using a VPN to connect to the internet, that is most likely the issue. Disconnect from the VPN or use another internet connection. The majority of other connectivity issues can be fixed by refreshing your page (control + R). If you are still having trouble, you can try a different browser or opening the webinar in an incognito tab. For audio issues, you can also click on the audio options at the top of the presentation to connect via a telephone.