Is your VPN turned on? If possible, please deactivate it.

If your network has a firewall set up, you may need to change the firewall settings to provide access to certain ports and domains. We are using Amazon Chime for video chat technology, and you can find the necessary ports and domains that need to be accessible below.

Ports for the calls
Destination: "99.77.128.0/18"

Domains that Chime needs access to
Destination
chime.aws
*.chime.aws
*."amazonaws.com "
"99.77.128.0/18"

You can find the source for this information, as well as further details on the following link:
"Network configuration and bandwidth requirements - Amazon Chime Help https://docs.aws.amazon.com/chime/latest/ag/network-config.html