Problem with Teams and Exchange Integration

Hi, 
you could check these, too:

1. Enable EWS at the Organization Level
Microsoft recently changed the behavior: Organization-level settings override user-level settings for EWS.
PowerShell Commands:
PowerShellGet-OrganizationConfig | fl EwsEnabledSet-OrganizationConfig -EwsEnabled $true

2. SSL Certificate Warning
An invalid or misconfigured SSL certificate can block communication between Teams and Exchange—especially for Autodiscover and EWS.
Check:
PowerShellGet-ExchangeCertificate | fl Issuer,CertificateDomainsShow more lines
Requirements:
Get-ExchangeCertificate | fl Issuer,CertificateDomains
SANs must include:
- mail.domain.com
- autodiscover.domain.com
CN (Common Name) must match the hostname.
No SSL offloading on the load balancer—SSL must terminate at the Exchange server.

3. Ensure External Autodiscover and EWS Are Reachable
Teams uses Autodiscover V2, which relies on Exchange Online redirecting to your on-premises server.
Test URLs:
https://autodiscover.domain.com/autodiscover/autodiscover.json
https://mail.domain.com/ews/exchange.asmx

4. Additional Checks
Get-AuthServer → Ensure OAuth is properly configured
Azure AD Connect: User must be synced
No SSL cipher suite mismatches (check load balancer settings)