Error: Strophe: BOSH-Connection failed: host-unknown

Hi, I have tried to add
https://github.com/jitsi/jicofo#secure-domain secure username and password for my site.

I did first 4 steps in the above link. I am not using jigasi, so i didn’t touch that part. I did everything as in the document.
After 4 th step, I restarted videobridge2 and jicofo, but I am getting this type of error in UI.

Error: “You have been disconnected”

In console: <Object.getGlobalOnErrorHandler>: UnhandledError: null Script: null Line: null Column: null StackTrace: Error: Strophe: BOSH-Connection failed: host-unknown
at Object.r.Strophe.log (VM88 lib-jitsi-meet.min.js:17)
at Object.error (VM88 lib-jitsi-meet.min.js:1)
at D.Bosh._connect_cb (VM88 lib-jitsi-meet.min.js:1)
at I.Connection._connect_cb (VM88 lib-jitsi-meet.min.js:1)
at D.Bosh._onRequestStateChange (VM88 lib-jitsi-meet.min.js:1)

and

VM133 app.bundle.min.js:126 2020-05-11T11:00:50.590Z [connection.js] <a.u>: CONNECTION FAILED: connection.otherError

Do I need to do step5 also in the above document, or I did anything wrong in previous steps.

I cloned jitsi meet using this link in ubuntu and using nginx.