I'm not near in right now but I wanted to answer the other questions. I'll check the http resoponse when I can.

1. Is your Jmp server's self signed certificate replaced with CA signed?

No I'm using all self signed certs. I setup a small lab to test this, previous labs didn't need real certs.

2. Are the jmp server services up? Try hitting this url from your browser https://<jmp-server-ip>/xmp/system/versions , it should return 200 OK.

thanks for this, going directly to the https://<jmp-server-ip> provides a 503 tomcat error if I remember, I'll try this url later

3. Is the horizon certificate  copied into "/vmware/jmp/com" folder as "horizon.cert.pem".

I have both the horizon and appvolumes certificates here, both self signed

4. Are you logged into horizon as domain/admin or are you using horizon servers local account?

using the domiain\admin account.

This is all in vmware workstation in two nested esxi servers so I'm not sure if thats related. Everything is on the same subnet.