Issue with SSL certificates Percona Server for Mongo DB

Team,

I am trying to configure SSL certificates for Mongo DB.   

I created CSR using below process.

openssl genrsa -out server.key 2048

 openssl req -new -key server.key -out server.csr

After submitted csr to our internal certificate Authority , i got three files. 

1) Hostname.cer

2) root_ca.cer

3) intermidiate_ca.cer

Then, i did cat server.key hostname.cer > server.pem

I configured server.pem & root_ca.cer in mongod.conf PEM file & CA file and started database instance. Instance is started successsfully. But when I try to make a connection,  It is failing. Below are the error log messages. Need your help to fix this ASAP.

 I tried it with PSMDB version 3.4 & 3.6. Both have the same errors. 

2018-11-23T15:43:40.192+0000 I NETWORK [listener] connection accepted from 10.198.219.64:40604 #1 (1 connection now open)
2018-11-23T15:43:40.197+0000 E NETWORK [conn1] SSL peer certificate validation failed: unable to verify the first certificate
2018-11-23T15:43:40.197+0000 I NETWORK [conn1] Error receiving request from client: SSLHandshakeFailed: SSL peer certificate validation failed: unable to verify the first certificate. Ending connection from 10.198.219.64:40604 (connection id: 1)
2018-11-23T15:43:40.198+0000 I NETWORK [conn1] end connection 10.198.219.64:40604 (0 connections now open)