16021: Failed to join conference due to account concurrency limit exceeded

A conference participant could not be created because your account was at or above its concurrent participant limit. This error is different from 16020, which is returned when a conference reaches maximum participant capacity.

• Your account reached the account-wide concurrent participant limit for Voice Conference. The default limit is 5,000 concurrent participants across all conferences in an account.
• Your application attempted to create conference participants before earlier participants had disconnected. Creating conference participants via the API counts toward concurrency.

• Retry the request after active participants disconnect and your account is back under the limit.
• Reduce the number of simultaneous conference participant creations in your application.
• If you regularly need more concurrent conference participants, contact your Twilio account team to request a higher limit.

• Voice Conference
• TwiML Voice: <Conference>