Everything installs as intended. Then when I try and do the initial log in as admin I get:

Internal Server Error
Call to undefined function simplexml_load_string()

An internal error occurred while the Web server was processing your request. Please contact the webmaster to report this problem.

Thank you.

I'm using Ubuntu 16.04.1 LTS

Any ideas?

Which LS version/build was used during the installation?

To me this looks like the php-xml package is missing in the php installation.
Do you maintain the ubuntu server? Or is there an admin?

Under ubuntu 16.04.X you can install the package via these commands:
sudo apt-get update
sudo apt-get install php-xml

php-xml is installed.
I am the admin for the linux server
the limesurvey build is 2.51.4

needed a reboot. It works now.
Thanks Jelo!

macintyres wrote: needed a reboot. It works now.

Glad for your that it works now.

Instead of a server reboot a restart of the apache is often enough to get it running after updates.
sudo systemctl restart apache2.service