What does HRESULT 0x80040015 (TAPI_E_INVALDIALPARAMS) mean?

TAPI_E_INVALDIALPARAMS

Invalid dialing parameters

TAPI_E_INVALDIALPARAMS is HRESULT 2147745813 (0x80040015) from Tapi3err.h. The documented description is “Invalid dialing parameters.” The result normally appears while creating or placing a call with provider-specific dialing timing and digit-control parameters. Its useful interpretation is precise: the dialing parameters is not valid for the exact provider, object, method, or lifecycle state that consumed it.

Owning component and lifecycle

• This result belongs to TAPI 3 address, call-control, phone, terminal, media-provider, request, or call-center processing.
• Associate this result with one concrete native method among ITTAPI, ITAddress, ITBasicCallControl, ITCallInfo, ITStream, ITTerminal, ITPhone, provider events, and Assisted Telephony.
• Before releasing objects after this result, retain provider identity, object instance, current state, requested transition, and the event sequence surrounding creating or placing a call with provider-specific dialing timing and digit-control parameters.

Plausible explanations

• It can occur when the caller supplies a malformed, unsupported, stale, or out-of-scope dialing parameters.
• It can also indicate that the dialing parameters belonged to another address, call, device, provider generation, user session, or COM object.

Choose among those branches only after comparing the failed dialing parameters with live capabilities or objects obtained from the same provider generation. A well-formed value can still be invalid because its scope, owner, state, or lifetime no longer matches the operation.

What to log before cleanup

• Record the HRESULT, 0x80040015, the native method, operation ID, elapsed time, process and thread IDs, application build, architecture, and COM apartment.
• Capture LINECALLPARAMS size and offsets, dial pause, digit duration, wait-for-dial-tone value, destination, and negotiated TAPI version.
• Keep provider version, address/call/phone/terminal identities, current state, requested state, object instance, and the first lower-level error that preceded it.
• Redact telephone numbers, credentials, recordings, user-user data, and directory attributes from telemetry while retaining lengths, types, hashes, ranges, capability flags, and opaque correlation identifiers.

Record whether the dialing parameters came from configuration, enumeration, user input, cached state, or a provider callback, and compare it with a freshly obtained object or value.

Reproduction and diagnosis

1. Capture the HRESULT at the first native return and identify the exact method used for creating or placing a call with provider-specific dialing timing and digit-control parameters.
2. Validate the dialing parameters without silently correcting it; check type, size, range, encoding, identifier scope, ownership, and lifetime as applicable.
3. Enumerate current provider capabilities or objects and compare them with the dialing parameters rejected by the failing call.
4. Reconstruct the event timeline before the failure to find removal, disconnect, cancellation, service restart, provider reinitialization, or another state transition.
5. Reproduce the failure with one object and one operation, then vary only the suspected field or state while tracking partial output and side effects.

Handling the result

The evidence-based correction is to rebuild the call-parameter block with initialized fields, validated offsets, and values inside provider capabilities. If the failure follows a provider, device, service, or configuration change, obtain a fresh object because an old interface or opaque identifier may remain invalid after recovery.

Practical example

For example, a copied call-parameter structure contains an old offset after a buffer resize; reconstructing the structure removes the invalid reference.

Related results

TAPI_E_INVALCALLPARAMS rejects the broader call-parameter structure; it isolates its dialing controls. Keep that distinction when building dashboards and exception mappings; otherwise input defects, lifecycle races, capacity limits, service outages, and final call outcomes collapse into one misleading category.

References

• Microsoft: TAPI_E constants — official Microsoft documentation used to interpret the HRESULT.
• Microsoft: lineMakeCall
• Microsoft: TAPI 3.1 Reference
• Microsoft: Telephony API interfaces