In most cases, black video on the endpoint is a result of Firewall/NAT issue. In some cases the firewall blocks the media ports and sometimes the endpoint doesn’t translate correctly the public/private addresses.

Firewalls block unsolicited incoming communications from outside the local network. Most firewalls are not designed to allow video conferencing scenarios where everyone is allowed to connect to everyone. 
Network Address Translation (NAT) is an Internet standard that enables a local-area network (LAN) to use one set of IP addresses for internal traffic and a second set of addresses for external traffic. A NAT box located where the LAN meets the Internet makes all necessary IP address translations. The NAT hides the internal native IP address and thus prevents incoming video calls to the devices on the private network.
UCAnyTime solves the issue while maintaining the security and advantages of firewall and NAT.

Most H.323 endpoints currently support the ITU H.460.18 and H.460.19 standards to enable traversal of firewalls. 
H.460.18 and H.460.19 are ITU standards which define protocols for the firewall traversal of signaling and media respectively.

In most cases the following will solve the issue:
Upgrading your codec to the latest version
Enable H.460 (Firewall/NAT Traversal) on the endpoint

Once this is done, you should be able to dial to the Virtual Room by using one of the following options:

Option 1: Register your endpoint the border controller/Gatekeeper (in this case
  • Use your Phone Number/ Conference Room Number as the E164 Number
  • Make sure H.460 is enabled
  • Dial to the Virtual Meeting Room only by dialing the virtual room number (e.g. 969123456789)
Option 2: Do not register the endpoint with the SCOPIA GK/Border Controller, or leave it registered to your local gatekeeper
  • Make sure H.460 is enabled
  • Dial to the Virtual Meeting Room using one of the following (depends on your endpoint model)
    • Virtual-Room@IP for example: 969111111111@
    • IP##Virtual-Room for example: