Xibo inable on displays

Good morning,

we have installed and configured xibo on our network monitors.
cms: https://sceve2016.xibo.co.uk

For a few days, we can not see the contents. The monitors / displays does not show the layouts.
A black screen with the xibo logo superimposed appears.

Monitor and xibo are connected to the network
The control panel shown the authorized and logged displays.

The layout is assigned.

Can you help me to solve the problem? why do not the displays show the contents of the layouts?
Thank you

This issue was supported in the Xibo Help desk. If the issue should return, please open a ticket and include all details relating to your issue.

Many Thanks.