Error code Connectivity_ICEWarn 0x80020 and Connectivity_ICEWarnEx 0x90

The MS Teams error codes "Connectivity_ICEWarn 0x80020" and "Connectivity_ICEWarnEx 0x9000" relate to ICE (Interactive Connectivity Establishment) issues, which affect real-time communications like calls and meetings. These codes originate from the underlying network protocols used to establish peer-to-peer connections in Teams (and other platforms using similar VoIP technology):

• Connectivity_ICEWarn 0x80020 typically points to DNS resolution problems. This means the Teams client cannot correctly resolve domain names required for setting up communication channels. Such a failure can prevent successful STUN/TURN connections, which are essential for media flow (audio/video/content sharing). The error often results from firewalls or proxies blocking certain traffic, network DNS misconfigurations, or lack of required network routes.
• Connectivity_ICEWarnEx 0x9000 is interpreted as a “malformed” condition in ICE connectivity checks. It may happen if network policies, firewall restrictions, or VPN configurations interfere with how connection candidates are formed and exchanged, or if traffic is intercepted or modified by security devices. This can block or disrupt the connectivity establishment for Teams calls and meetings.

Troubleshooting Tips:

• Ensure your firewall and proxy allow traffic for WebRTC, STUN, and TURN protocols (UDP ports 3478–3481, as well as dynamic media ports and TCP 443).
• Check if NAT traversal is properly configured (especially with company VPNs or networks using strict controls).
• Try Teams on a different network to rule out local restrictions.
• Update Teams and network drivers.