After doing a CDS migration and splitting into two on prem locations, the list of organizations is empty after associating the organizations together.
Developer tools in the web browser show possible time outs on the networking.
There may be an error in the console of the developer tools that shows:
Uncaught TypeError: I is null.
Cloud Director 10.5.1.1
This seems to be caused by potential network latency between the SaaS service and the two sites.
Make sure that the network is not currently under a load that increases latency between the sites.