Regus serviced offices block VoIP traffic by default which means your hardware or software phone can't access any VoIP providers network.
They permit the traffic upon request and will direct you to an online form on their website where you enter the MAC (Media Access Control) address's for each of your devices. Once you input these everything works perfectly!
MAC Address's are the physical address your device has on a network. It's easily identified on most phones as its printed on a sticker you can find somewhere on the handset. For softphones and/or smartphones, you'll need to get the MAC address of your device from the devices user interface.
To find a Windows computer MAC address:
1) Navigate to the "Command Prompt". This can be found in your main menu or by selecting "Run" from the main menu and typing "Cmd".
2) Once at the prompt, type "ipconfig /all" and press enter
3) This will show you all your active network interfaces. Find the correct interface for your connection to the Internet (eg: WiFI Adaptor or Ethernet network card)
4) The MAC address will be shown below the relevant connection following the words "Physical Address"
To find an Apple Mac computer MAC address:
1) Click on the Apple icon in the top left corner and select System Preferences
2) Click on Network
3) Select the interface you are using to connect to the Internet from the left. These are normally shown in green as the active connections.
4) Click on Advanced in the bottom right and then select the Hardware tab.