Our client had a SharePoint outage where we were unable to reconnect their SharePoint server to the farm. It is a single server farm and they use Nintex Workflows for one of their processes. 

We were forced to start with a new SharePoint installation and then mounted the old Content database which allowed us to get to all of their content. 

After this, Nintex is no longer available in the menus and there are errors relating to workflows.

What is the solution to get the Nintex workflows running again?