Forum Discussion

BenConrad's avatar
BenConrad
Copper Contributor
Sep 30, 2025

Network connectivity test TCP Connection results unreliable

My team has spent the last 2 business days trying to get the https://connectivity.office.com/ TCP connection test to complete successfully to appease the Microsoft Unified Support Team.  They don't want to take our MS Teams crash diags until they see SSL Interception Detection and TCP connection tests passing successfully. 

We can't get TCP connection tests to pass, we get one of the following:

  • Success
  • Attempt #1 Success, Attempt #2 Failure
  • Any number of errors to unblock URLs such as (but not limited to) ocsp.digicert.com,ocspx.digicert.com,ocsp.omniroot.com,su.symcb.com,sr.symcb.com,sd.symcb.com,s1.symcb.com,sa.symcb.com

We figured it was something with the corporate network but that's not the case.  Last night we had about 50 employees try this test from their home (personal) computers that have no connection to our corporation. 

The TCP Connection test fails on home (consumer) PCs.

What's the story with this TCP Connection check?

deployment
Network connectivity
networking

2 Replies

  • Jrbedford's avatar
    Jrbedford
    Copper Contributor
    Feb 06, 2026

    Hi BenConrad​ -- Did you ever resolve this or figure out the cause?

    My org is seeing the same issues...

    We aren't trying to diagnose any specific issues with any of our devices, though... just trying to get this test to run clean or figure out why it isn't. Our devices appear to be working as expected.

  • Kidd_Ip's avatar
    Kidd_Ip
    MVP
    Sep 30, 2025

    Consider this:

     

    1. Whitelist Microsoft 365 Endpoints

    Ensure your firewall, proxy, or endpoint security software allows traffic to all Microsoft 365 URLs and IPs.

    1. Disable SSL/TLS Inspection

    If you’re using any kind of SSL inspection (even at home via antivirus), disable it for Microsoft endpoints. These include:

    • *.microsoft.com
    • *.office365.com
    • *.digicert.com
    • *.symcb.com
    1. Use a Clean Test Environment

    Try running the test from a clean Windows install with no antivirus, VPN, or proxy settings. Use a wired connection if possible.

    1. Check DNS Resolution

    Use a reliable DNS provider like Google (8.8.8.8) or Cloudflare (1.1.1.1) to ensure proper resolution of OCSP endpoints.

    1. Run the Test Authenticated

    Sign in to the test site with your Microsoft 365 account. This can improve accuracy and provide tenant-specific diagnostics.

Resources