Central backupplan not executet on agent

On some machines the central backuplan will not be executed if I start it.
The plan is also not visible if I cannot to the agent machine. On one machine the issue solved itself (no idea why when) on another machine even after several hours the plan is not known by the agent. Any help how I can analyse the issue would be appreciated.

Version used is Acronis 11 Advanced Workstation Build 17217