troubleshooting — error catalog

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Every article leads with the root cause, shows you what to check, and gives you a manual fix that actually works — whether you ever become a customer or not. No forms, no sales follow-up.

SBC integration errors

AudioCodes 403 Forbidden: Microsoft Teams Direct Routing TLS connection rejected

Teams Direct Routing calls fail instantly; SBC log shows 403 on the TLS connection to sip.pstnhub.microsoft.com.

FIX VERIFIEDMANUAL FIX INSIDE

Ribbon SBC 504 Gateway Timeout: Zoom Phone trunk shows offline

Zoom Phone dashboard reports the customer's trunk offline; Ribbon logs 504 Gateway Timeout on inbound signaling.

FIX VERIFIEDMANUAL FIX INSIDE

anynode SBC fails to resolve sip.pstnhub.microsoft.com (DNS)

anynode on an Azure VM logs "failed to resolve sip.pstnhub.microsoft.com"; Teams Direct Routing registration fails or flaps.

FIX VERIFIEDMANUAL FIX INSIDE

Teams Direct Routing TLS handshake failure: Ribbon Edge cipher suite mismatch

TLS handshake to sip.pstnhub.microsoft.com fails with handshake_failure alert from a Ribbon Edge SBC.

FIX VERIFIEDMANUAL FIX INSIDE

Router & ISP SIP ALG issues

How to disable SIP ALG on the Comcast Business Gateway DPC3941B

Remote workers behind a Comcast DPC3941B get one-way audio or calls that drop at exactly 32 seconds.

FIX VERIFIEDMANUAL FIX INSIDE

Bypass SIP ALG on a Spectrum Ubee router: home-worker VoIP drops and one-way audio

Spectrum Ubee gateway: remote worker's calls drop at 32 seconds or land with one-way audio.

FIX VERIFIEDMANUAL FIX INSIDE

AT&T Fiber Pace 5268AC: SIP ALG rewriting causes dropped calls at 32 seconds

Calls through an AT&T Pace 5268AC gateway drop at exactly 32 seconds; one-way audio on others.

FIX VERIFIEDMANUAL FIX INSIDE

Certificate automation on legacy SBCs

Automate Let's Encrypt certificates on TE-SYSTEMS anynode (Azure VM)

90-day manual certificate grind on anynode; one missed renewal takes a whole office's voice offline.

FIX VERIFIEDMANUAL FIX INSIDE

AudioCodes Mediant VE: automated wildcard SSL certificate renewal with Let's Encrypt

Uploading renewed certificates to a Mediant VE through the Web GUI every 90 days, per tenant.

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How to run a Let's Encrypt ACME client for a Ribbon SBC (you can't — do this instead)

Trying to install certbot or acme.sh on a Ribbon SBC itself; the hardened OS won't allow it.

FIX VERIFIEDMANUAL FIX INSIDE
This catalog grows weekly from the error list our own engineers hit. More router models, more carrier quirks — if the error you're fighting isn't here yet, the free tools below will still isolate it in minutes.