I have same quesion , I install a nsx-t 2.4.1 in one cloud , for limited storage , only build one mananger/controller . then install edge and pks ops .

After a storage full issue , restart nsx-t manager  show the same error in web UI/

In the syslog for nsx-manager ; error include:

80>1 2019-09-11T06:22:05.261Z nsxtm1 NSX 3555 - [nsx@6876 comp="nsx-manager" subcomp="node-mgmt" username="root" level="WARNING"] Connection to cbm refused or timed out: 111

<179>1 2019-09-11T06:22:05.263Z nsxtm1.corp.local NSX 5517 - [nsx@6876 comp="nsx-manager" errorCode="MP2101" subcomp="policy"] Request GET http://localhost:7441/api/v1/cluster-manager/config HTTP/1.1 failed, return code is 503

<179>1 2019-09-11T06:22:05.263Z nsxtm1.corp.local NSX 5517 - [nsx@6876 comp="nsx-manager" errorCode="MP2123" subcomp="policy"] Cluster config retrieved from cluster manager is empty.

<180>1 2019-09-11T06:22:05.282Z nsxtm1 NSX 3555 - [nsx@6876 comp="nsx-manager" subcomp="node-mgmt" username="root" level="WARNING"] Connection to cbm refused or timed out: 111

<179>1 2019-09-11T06:22:05.283Z nsxtm1.corp.local NSX 5064 - [nsx@6876 comp="nsx-manager" errorCode="MP2101" subcomp="manager"] Request GET http://localhost:7441/api/v1/cluster-manager/config HTTP/1.1 failed, return code is 503

<179>1 2019-09-11T06:22:05.283Z nsxtm1.corp.local NSX 5064 - [nsx@6876 comp="nsx-manager" errorCode="MP2123" subcomp="manager"] Cluster config retrieved from cluster manager is empty.