NFS appliance fails to mount NFS share, when UDP is disabled from NFS-server

Issue

Attempting to mount a NFS share, hosted in RHEL, from an appliance, is failing; The following is observed from the appliance log:

<hostname> user.notice kernel: nfs: server XX.X.X.XX not responding, timed out
<hostname> user.notice kernel: nfs: server XX.X.X.XX not responding, timed out  <---
<hostname> daemon.notice root: Waiting to retry mount of XX.X.X.XX:/path/to/share using nfs... 
<hostname> daemon.notice root: Attempting mount of XX.X.X.XX:/path/to/share using nfs...
<hostname> user.warn kernel: nfs warning: mount version older than kernel
<hostname> user.notice kernel: nfs: server XX.X.X.XX not responding, timed out
<hostname> user.notice kernel: nfs: server XX.X.X.XX not responding, timed out
<hostname> daemon.err root: Unable to mount drive after 2 attempts  <---

This used to work when the NFS server was hosted on a non-RHEL environment. The above indicates a connectivity issue between the server and the appliance, due to which the mount operation is timing out, and the mount is eventually failing.