Challenge
The error "Connection problems" appears with vCenter server or ESX(i) host in Veeam Monitor infrastructure view. vCenter server or the ESX(i) host becomes grayed out:
No data goes to the Veeam Monitor client and into the Veeam Monitor database. vCenter server or ESX(i) might be disconnected constantly in the Veeam Monitor Client.
Also you may see gaps on real-time performance graphs in the Veeam Monitor client.
Cause
By default, Monitor requires server time to be less than a 5 minute difference between the Veeam Monitor Server and the VC or host that is having this issue. You will also see the following error in the logs:
"Collecting thread has failed to initialize (Time difference between Veeam Monitor server and ESX host is too large. Make sure that NTP is enabled on ESX host and try again.) and will be stopped"
Solution
Make sure to have the time difference between Veeam Monitor and the host or VC having the issue no more than 5 minutes. This is achieved through NTP or other time protocols in one's environment.
since v6.0 it is possible to modify the maximum allowed time difference by manually creating or modifying if exists the MaxTimeDiff value under HKEY_LOCAL_MACHINE\SOFTWARE\Veeam\Veeam ONE Monitor\Service on Veeam One server and setting it to preferred in seconds > restarting Veeam One Monitor Server service.
More Information
For v5.x
If you right click on a host or VC that is grayed out and select "Get Error Message", Monitor will return useful information for Veeam's KB's.
If you have any questions, contact Veeam Support.