I'm running Linux Mint 19 Tara 64-bit, Kernal Linux 4.15.0-20 generic x86_64, Mate 1.20.1.

All of a sudden I have lost the ability to connect to my SMB share on this machine. I was copying data over to it just fine and now I can't anymore. The client that I'm using is a Windows 10 and an Android. Before all this happened I had copied like 40GB of data already. I tried a simple restart but that Didn't work. What the hick would just make the SMB share not accessible anymore?

This is what I did to create the share (that was working).
• Install Samba
○ sudo apt-get update
sudo apt-get install samba
• Set a password for your user in Samba
○ sudo smbpasswd -a <user_name>
• Create a directory to be shared
mkdir /home/<user_name>/<folder_name>
• Make a safe backup copy of the original smb.conf file to your home folder, in case you make an error
sudo cp /etc/samba/smb.conf ~
• Edit the file "/etc/samba/smb.conf"
sudo nano /etc/samba/smb.conf
Once "smb.conf" has loaded, add this to the very end of the file:

[<folder_name>] - make sure you use [] around the share name
path = /home/<user_name>/<folder_name>
valid users = <user_name>
read only = no

Restart the samba:
sudo service smbd restart

In fact, I can't share with the GUI either using "Share Options".

Yes, I am on the same network.

What do you mean by lost the ability to connect? Does file explorer still show the network drive?
In a windows cmd box you can run some quick checks to see if the Windows PC is still connected to the share. The net command show the network drive and its status.

net use

net view \\mint_pc_host_name

From the Mint PC you can use the smbclient utility as a quick check. You might have to install the cifs-utils.

smbclient -L localhost -U user_name
Enter the user_name's password and the output should show the share.

In addition by default the [homes] share will automatically create shares for every use i.e path=/home/user_name by default. Just uncomment the [homes] section and restart samba.

Also apt-get update is used to synchronize the package index files from their sources. apt-get upgrade is used to install the newest versions of all packages.

I assume that /home is on the RAID or other large partition so that running out of space isn't a factor...

I fixed it....kind of. I reinstalled an older version of Linux Mint (18.3). Everything seems to be working now.

I had a RAID configuration last time. Maybe I changed some setting that messed up the smb share.