opscenter server: Master servers partially connected

Opscenter server version: 7.6.0.1

OS version: Win2k8R2 Enter x64

Issue: Data collection Failed for: Scheduled Jobs, Retention Level

I presently have 3 master servers connected to my opscenter environment. Recently all 3 servers are showing partially connected: Data collection Failed for: Scheduled Jobs, Retention Level 

I had tried disabling and re-enabling data collections, but issues persisted. Closer look shows following errors applicables to all the 3 master server

Data collection has failed because of unknown reason

Please advice