Rstudio Server: [Rserver] Error System Error 2

I am trying to install RStudio server on my Ubuntu server. The installation seems to be fine but when I run the command:

sudo rstudio-server verify-installation

It does not return anything. Then I tried running the command:

sudo rstudio-restart
    rsession: no process found

I have looked at some other posts with similar problems and it seems mostly it is recommended to disable AppArmor, but when I attempt to do this with the following commands I get these errors:

sudo ln -s /etc/apparmor.d/rstudio-server /etc/apparmor.d/disable/
    ln: failed to create symbolic link '/etc/apparmor.d/disable/rstudio-server': File exists

sudo apparmor_parser -R /etc/apparmor.d/rstudio-server
    File /etc/apparmor.d/rstudio-server not found, skipping...

It didn't appear as though I actually disabled apparmor but I reloaded AppArmor anyway like this:

sudo invoke-rc.d apparmor reload

After reloading AppArmor, I tried to run the verify-installation command again and get the following output:

sudo rstudio-server verify-installation
    26 Mar 2018 16:52:16 [rserver] ERROR system error 2 (No such file or directory) [path=/var/lib/rstudio-server/secure-cookie-key]; OCCURRED AT: rstudio::core::Error rstudio::server::key_file::readSecureKeyFile(const string&, std::string*) /home/ubuntu/rstudio/src/cpp/server/ServerSecureKeyFile.cpp:55; LOGGED FROM: int main(int, char* const*) /home/ubuntu/rstudio/src/cpp/server/ServerMain.cpp:435

I then tried looking at posts about this type of problem and I came across one that said: Can you check the permissions on that /var/lib/rstudio-server directory and make sure its readable (and see if there is a secure-cookie-key file in it)?

The /var/lib/rstudio-server directory is owned buy root and has 755 permissions. I then checked the contents of the directory and this is what I have:

drwxr-xr-x 2 root root 4096 Feb 16 14:38 body
drwxr-xr-x 2 root root 4096 Feb 16 14:38 conf
drwxr-xr-x 2 root root 4096 Feb 16 14:38 proxy
-rw-r--r-- 1 root root 63544178 Mar 12 11:37 rstudio-server-1.1.442-amd64.deb
-rw------- 1 root root 0 Mar 26 09:57 secure-cookie-key

I'm really at a loss now as to what my problem is. Can anyone shine some light on this situation?