3CX WebMeeting Troubleshooting


Unable to Join (Participant)

Unable to Join (Meeting Host)

If you’re the PBX Administrator

Did you recently change the country code of your license key?

Old PBX with the same license key still running?

Have you unbound the FQDN from your license key?

Restrictive Outbound Firewall?

Force Meeting Resynchronization

Update to the latest PBX version

Network Lockdown

Using WebMeeting - MCUs

Using WebMeeting - CDN, Temp Storage, Proxies

PBX - Meeting Sync

PBX - Dial-In


Trying to connect to your colleagues but instead, you’re faced with an error message? Not to worry! In this document we cover some common troubleshooting issues and how to address them:

Unable to Join (Participant)

The most common cause is that the meeting you are trying to join has not yet started, has ended already or has been canceled by the host. Try the meeting invitation once more; if the result is the same we suggest you contact the meeting host to check or see if you can reschedule for a later date.

Unable to Join (Meeting Host)

If you are the host of the meeting, ensure that:

  • You have not deleted the meeting
  • The meeting link doesn’t belong to a meeting that has already ended 

Try to schedule a new meeting from your 3CX Web Client. If the issue persists please contact the administrator of your PBX and make reference to this document.

If you’re the PBX Administrator

If your team (extensions) experience this on a regular basis, check the following scenarios:

  1. Did you recently change the country code of your license key?

If so, scheduled meetings might not have been recreated in the new time-zone yet. To recreate all scheduled meetings go to the 3CX Management Console, restart the “3CX System Service” and wait 10 minutes. This synchronizes your meetings with the new time-zone. Existing and future meetings will function as planned after this synchronization.

  1. Old PBX with the same license key still running?

Did you just make a new PBX installation using a key that’s being used by another PBX? Unless the second PBX is a correctly set up failover (as per 3CX guidelines), then issues such as ‘Meeting not found’ will occur. To resolve this and other issues, power down or uninstall one of the 2 PBXs or set it up for failover.

  1. Have you unbound the FQDN from your license key?

3CX WebMeeting cannot function if your installation has not been mapped to an FQDN. You can check whether or not your license key is bound to an FQDN from the customer portal (https://customer.3cx.com). If it’s not bound, then you must rebound an FQDN to your license key. This is done during the installation of your PBX. Please note that all scheduled future meetings are canceled during the unbound process.

  1. Restrictive Outbound Firewall?

3CX WebMeeting cloud platform must be reachable from your PBX. In case outbound connections are filtered by your corporate firewall, create an allow-egress-rule to “webmeeting-director.3cx.net”, transport TCP, port 443. It is strongly advised not to take the current NSlookup IPs as allowed destinations. Those might change without any given notice.

  1. Force Meeting Resynchronization

Restarting the 3CX System Service in your PBX forces your PBX to retry resynchronizing all meetings with our webmeeting platform. The System Service is a non critical service which will not interrupt calls. Some email sending capabilities and other non-call related functions will be affected while this service restarts.

  1. Update to the latest PBX version

Take a look at the PBX changelog. Often, there are changes in the PBX related to WebMeeting functionality that may change how WebMeeting synchronization works. Fixes and improvements in newer versions of the PBX may solve issues you’re experiencing.

Network Lockdown

If internal workflows and processes require strict firewall rules to be in place, this can be achieved by using the information below. Whitelist all IPs returned when performing nslookup towards the following FQDNs. Note that these FQDNs and IPs may change without prior notice.

  1. Using WebMeeting - MCUs

End users connect to MCUs. Media is sent to and received from MCUs for meetings to work.

  • mcu-zone-a.3cx.net
  • mcu-zone-b.3cx.net
  • mcu-zone-c.3cx.net
  • mcu-zone-d.3cx.net
  • mcu-zone-e.3cx.net
  • mcu-zone-f.3cx.net
  • mcu-zone-i.3cx.net

UDP: 48000-65535

TCP: 443

  1. Using WebMeeting - CDN, Temp Storage, Proxies

The servers below are used for fast proxied access to the WebMeeting UI, recordings and file uploads worldwide.

  • wm-cdn.3cx.net
  • recording.3cx.net
  • uploads.3cx.net
  • webmeeting-director.3cx.net

TCP: 443 / HTTPS

  1. PBX - Meeting Sync

Meetings created on your PBX are synced to 3CX WebMeeting servers where they are freely served from with high uptime and user capacity.
For synchronization to occur, the following FQDNs must be whitelisted.

  • zone-a.3cx.net
  • zone-b.3cx.net
  • zone-c.3cx.net
  • zone-d.3cx.net
  • zone-e.3cx.net
  • zone-f.3cx.net
  • zone-i.3cx.net
  • webmeeting-director.3cx.net

TCP: PBX MyPhone Port (Typically 5001 or 443)

  1. PBX - Dial-In

Meeting dial-in users connect to your own PBX which then transmits and receives RTP data from/to the MCU servers below.

  • mcu-zone-a.3cx.net
  • mcu-zone-b.3cx.net
  • mcu-zone-c.3cx.net
  • mcu-zone-d.3cx.net
  • mcu-zone-e.3cx.net
  • mcu-zone-f.3cx.net
  • mcu-zone-i.3cx.net
  • webmeeting-director.3cx.net

UDP: 10500-10999

TCP: PBX MyPhone Port - Typically 5001 or 443