Android Teams login fails during ADFS federation with SSL error

Hello

Android mobile users cannot sign in to Microsoft Teams

The login fails during the ADFS federation step due to an SSL error

Environment

Android OS versions 10 to 14

Microsoft Teams mobile app

Entra ID federated with on premises ADFS

ADFS service URL is masked

Public certificate issued by Sectigo

Issue description

After entering the account in Teams the sign in process redirects to ADFS

The page does not load correctly and shows infinite loading or a blank screen

The same account works normally on PC browser PC Teams and Outlook Web

The issue occurs only on Android mobile apps that use WebView

Android log summary

OAuth2 WebView client received SSL error

Primary error SSL untrusted

Wildcard certificate for masked domain

Certificate issued by Sectigo Public Server Authentication CA

Troubleshooting performed

Device date and time verified

Teams app cache cleared and app reinstalled

Issue reproduced on multiple Android versions and devices

PC authentication works with the same certificate

Questions

Can Android WebView or Microsoft mobile authentication fail with SSL untrusted when the ADFS server does not provide a complete certificate chain

Is full chain certificate configuration required on ADFS IIS for mobile authentication

Can SSL inspection or proxy interception cause this issue only on Android apps while PC browsers work normally

Are there official Microsoft recommendations for certificate configuration when using ADFS federation with Android mobile apps

Additional information

The same behavior occurs in other Microsoft mobile apps

The suspected causes are incomplete certificate chain or network SSL inspection

Thank you