### Answer --- If callers are getting busy tones when an agent is already on a call, there are a few things to check: Concurrency Limits If you're hitting your plan's concurrency limit, calls will fail with

concurrency_limit_reached

. [(1) ]() You can verify this by checking the call history and detailed log for the disconnection reason. [(2) ]() Potential Platform Issues There have been instances where users experienced similar symptoms (agents not answering, busy signals) due to temporary platform outages—for example, a ~25 minute LiveKit outage caused

dial_failed

errors and 486 "user busy" responses for SIP trunking users. [(3) ]() Recommended Steps 1. Check your call history dashboard for the specific disconnection reason and SIP error code. [(2) ]() 2. Check [) for any ongoing incidents. [(3) ]() 3. If using custom telephony/SIP trunking, verify your configuration is correct. [(2) ]() If the issue persists and isn't related to concurrency limits or a platform outage, consider reaching out via [Contact Sales]() or checking [) for additional support.

​ To learn more, see the sources I considered: [[1] Debug call disconnection](https://docs.retellai.com/reliability/debug-call-disconnect) [[2] Debug outbound connection issues](https://docs.retellai.com/reliability/debug-outbound-call) [[3] Agents not answering - https://status.retellai.com/ not showing any outages](https://discord.com/channels/1186424376300679209/1394440925131833526) ​

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.