First we will want to verify the connection the Collectors have to the vCenter.
- First go onto the Collector server and verify the service ‘Veeam VMware Collector’ is running
- After that verify the credentials are correct. You can do that by following this link in the user’s guide https://helpcenter.veeam.com/mp/80/vmware_guide/index.html?basic_configuration_launch_web_ui.html
- After this has been verified it may be a good time to analyze if you need to add more collectors. If this error started happening after you added a host or some VM’s then it may be required. Using the install media for Management pack you can run a collector only installation on a server to see If this resolves the issue or you can deploy the collector through SCOM as well.
This link below will help you with the collector only installation.
Usually these steps will resolve the issue. The most common solution is having to add additional collectors. If these steps did not work, then please create a ticket with support.