Configuring Plex Remote Access with NAS device

> Model: R6220|AC1200 Smart WiFi Router with External Antennas

   Firmware version?  Connected to what?

> [...] I am running a Plex server on a NAS device (the one I have is
> called my cloud home) [...]

   Many things are.  Western Digital?  An actual model number would make
for a more useful description.  (One of us might want to find the
relevant documentation for it.)

> [...] I am unable to successfully configure the remote access feature.
> [...] this did not work. [...] tried manually port forwarding [...]

   None of "unable" or "did not work" or "tried" is a useful problem
description.  It does not say what you did.  It does not say what
happened when you did it.  As usual, showing actual actions (commands)
with their actual results (error messages, LED indicators, ...) can be
more helpful than vague descriptions or interpretations.

   Whether the configuration is automatic (UPnP) or manual (port
forwarding), many of the potential problems are similar.  For the usual
problems with port forwarding, see:

      https://community.netgear.com/t5/x/x/m-p/1859106

   If more advice is desired, then adding some actual IP addresses and
error messages to your description might help.  If you're worried about
revealing secrets (like, say, a public IP address), then the top half of
the address, "a.b" out of "a.b.c.d", would satisfy most of my curiosity.
Or, plug that address into the form at: https://whois.arin.net/ , and
see if it is a public or private address.