@ituni 

Can you share your /etc/hosts from the 2 servers? many a time member forget very trivial things ib your /etc/hosts on uvmu02.uvmu0x.com should look like this don't comment

127.0.0.1 localhost
127.0.1.1 uvmu02.uvmu0x.com # This one

# The following lines are desirable for IPv6 capable hosts
::1 ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters

# uVMU0X
192.168.56.101 uvmu01.uvmu0x.com uvmu01
192.168.56.102 uvmu02.uvmu0x.com uvmu02
192.168.56.103 uvmu03.uvmu0x.com uvmu03

Assuming the Ambari server is uvmu01.uvmu0x.com firstly I would like you to check that the ambari server and agent are of the same version

# rpm -qa|grep ambari

On server uvmu02.uvmu0x.com

Thereafter share ensure you disabled the Firewall

$ sudo ufw disable

Confirm the Firewall stopped and disabled on system startup

$ sudo ufw status

$ sudo apt-get install ambari-agent

Share your ambari-agent.ini it should look like this on all nodes I even the one hosting Ambari I am wondering why your second server has hostname=uvmu02.uvmu0x.com in the Ambari-agent.ini????

[server]
hostname=uvmu01.uvmu0x.com
url_port=8440
secured_url_port=8441
connect_retry_delay=10
max_reconnect_retry_delay=30

$ ambari-agent start

Now go back to the Ambari UI and choose manual registration your uvmu02.uvmu0x.com should now register successfully

Please revert