If you’re unable to make or receive Voice calls, calls are being routed unexpectedly, or call details are missing, this article explains the most common causes and how to resolve them.
Voice calls rely on several settings working together, including your phone number status, call permissions, routing settings, microphone access, network connection, and wallet or Twilio account status.
Before you begin
Before troubleshooting a specific issue, check that:
- Voice calls are enabled for your workspace and phone number.
- The phone number supports Voice calls.
- You have permission to make or receive calls.
- Your internet connection is stable.
- SleekFlow has permission to access your microphone.
- Your browser, device, VPN, firewall, or company network is not blocking the call connection.
If you purchased the phone number via SleekFlow
Check that:
- Teammates have the appropriate permissions to make, receive, or manage calls.
- Your SMS and Voice Wallet balance is at least US$15.
You won’t be able to make outbound calls when the wallet balance falls below US$15.
If you’ve connected your own Twilio number
Check that:
- The phone number supports Voice calls
- Your Twilio account is active
- Billing is enabled in Twilio
- The phone number is successfully connected to SleekFlow
Charges for calls made with your own Twilio number are handled by Twilio and are not deducted from your SleekFlow SMS and Voice Wallet.
Common voice call error codes
⚠️ Note
The list below includes the most common error codes. These are the ones most likely to appear when making or receiving voice calls via SleekFlow.
For all other codes, see this full list of error and warning.
The table below covers the Voice call errors you’re most likely to encounter. Include the error code when contacting SleekFlow Support.
| Error code | Description | Possible cause and suggested solution |
| 31000 | General call error |
The call may have been interrupted by an unstable network, VPN, firewall, or temporary connection issue. Refresh SleekFlow and try again. If you’re using a VPN, disconnect it before retrying. Contact Support if the issue continues. |
| 31001 | Call setup unavailable | The Voice call configuration may be incomplete or unavailable. Contact SleekFlow Support. |
| 31002 | Connection declined | The call request may have been rejected because of a temporary connection or account issue. Try the call again. Contact Support if this happens repeatedly. |
| 31003 | Connection timed out | The connection may be slow, unstable, or unable to reach the Voice service. Check your internet connection and try again. |
| 31005 | Connection interrupted | Your browser may have lost its connection because of an unstable network, VPN, firewall, or company network restriction. Check these settings, then try again. |
| 31009 | Unable to connect | Your browser or network may be blocking the connection required for Voice calls. Check your network, browser restrictions, VPN, and firewall settings. |
| 31100 - 31105 | Invalid call request | The call request may contain outdated or incomplete setup information. Refresh SleekFlow or sign in again. Contact Support if the issue continues. |
| 31201 - 31207 | Account authorization error | Your session may have expired, the account may be inactive, or a request limit may have been reached. Refresh SleekFlow or sign in again. Contact Support if the issue continues. |
| 31208 | Microphone access blocked | Your browser or device has blocked SleekFlow from using the microphone. Allow microphone access in your browser or device settings, then refresh the page. |
| 53000 | Signaling connection failed | Your network, VPN, firewall, or company network may be blocking the signaling connection required to start the call. Check these settings and try again. |
| 53405 | Audio connection failed | Your microphone, speaker, network, VPN, or firewall may be affecting the call audio. Check your audio devices and network settings, then try again. |
Troubleshooting common voice issues
Unable to make an outbound call
If you’re unable to make a call, check the phone number, your permissions, and your connection.
| Check | Suggested solution |
| Phone number and permissions | Confirm that the selected phone number supports Voice calls and that you have permission to make calls. |
| Contact’s phone number | Make sure the phone number is valid and includes the correct country code. |
| SMS and Voice wallet or Twilio account |
If you have purchased the phone number via SleekFlow, make sure your SMS and Voice wallet balance is at least US$15. If you connected your Twilio number to SleekFlow, go to Twilio and check the number and Twilio account are active. |
| Microphone and connection | Allow microphone access and check that your internet connection is stable. Disconnect your VPN and try again. |
Unable to receive an inbound call
If incoming calls aren’t ringing, check the phone number’s routing settings and your availability.
| Check | Suggested solution |
| Phone number status |
Confirm that the selected phone number supports Voice calls and that you have permission to make calls.
Refer to this article to learn more about roles and permissions: Roles and permissions |
| Inbound routing |
Check that incoming calls are routed to the correct teammate, team, or contact owner.
Refer to this article to learn how to make and receive calls, and configure call routing: Voice call overview |
| Team permissions |
Confirm that you can receive calls and belong to the selected team, where applicable.
Refer to this article for more details: Voice call overview |
| Notification and connection | Allow call notifications and microphone access. Disconnect your VPN and test again. |
⚠️ Note: If the caller can’t be matched to a contact, or the contact doesn’t have an assignee, the call is sent to the Call Inbox. It won’t trigger an incoming-call pop-up.
Contact SleekFlow support
ℹ️ You can contact SleekFlow customer support by emailing cs@sleekflow.io
Contact SleekFlow Support if the issue continues after you’ve completed the troubleshooting steps above.
To help us investigate, please include the following in your enquiries:
- Your workspace name or ID
- The affected phone number
- Whether the number is managed by SleekFlow or connected from Twilio
- Whether the issue affects inbound or outbound calls
- The approximate call time and timezone
- The contact or phone number involved
- A screenshot of the error message or code
- Whether you’re using the web or mobile app
- Whether you’re connected through a VPN, firewall, or company network
For a number connected from Twilio, also confirm that the number supports Voice calls and that the Twilio account is active.