Constant script/application for shared drive checking/mounting
You can do this in the shell.

Launch a Terminal, then run:

mount


Find the line with your volume, and grab the first part up until the space. 
It should look something like:

//warren@10.0.15.2/Shared%20Network%20Volume


Thats username@IP_OF_NAS/VolumeName

Now here is the script, save it as "remount.sh"

#!/bin/bash

date
mounted=$(/sbin/mount | grep -c "VOLUMENAME")
if [ $mounted -eq 0 ]; then
   ping -q -c 2 -t 1 IP_ADDRESS &gt; /dev/null 2&gt;&amp;1
   if [ $? -eq 0 ]; then
      if [ ! -d "/Volumes/VOLUMENAME" ]; then
         mkdir "/Volumes/VOLUMENAME"
         chown LOCALLOGIN:staff "/Volumes/VOLUMENAME"
      fi
     su LOCALLOGIN -c "/sbin/mount -t afp afp://YOURLOGIN:PASSWORD@IP_ADDRESS/VOLUMENAME /Volumes/VOLUMENAME"
   fi
else
   echo "Already mounted"

fi


You need to change the variables in all CAPS above.

YOURLOGIN (Your login on the NAS)
PASSWORD (Your password on the NAS)
LOCALLOGIN (Your local login on the MAC machine)
IP_ADDRESS (the IP ADDRESS of the NAS)
VOLUMENAME (The Volume Name on the NAS)


Unmount the network volume that you previously mounted, then run:

chmod 755 remount.sh
sudo ./remount.sh


Make sure this mounts the volume OK.  It worked fine on my MacBook running Sierra against an Apple Time Capsule.

Now if all is well, we add it to cron to run it as root (sudo) every 15 minutes.

sudo crontab -e


Add something like this (season to taste):

*/15 * * * * /Users/warren/remount.sh &gt;&gt; /Users/warren/remount.log 2&gt;&amp;1


You'll note I saved the script in my home directory.  If you are tidy, you probably don't want to save it there.

Dismount the volume, and wait 15 minutes and see if it reappears.  If not, look at the log file to see whats up.