On Windows 7 PC.
Uninstalled Version 1.80, installed Version 1.81. The server does not find any renderer. Red cross appears.
Restarting the server - doesn`t help.
Deletion of the config file would fix the problem for one time only - server found renderers and started, but after closing and restarting the red cross appeared again.
Downgrade to 1.80 (including deletion of the config file): Everything works again without any issue.