A few weeks back we ran into two cases where users were unable to install Nintex RPA in their environment.  One case was unique as it would start the process of install and right after it completed it would start the uninstall process.  After pulling our hair for sever days, customer reached out to their IT department to see if there is anything unique within their environment and sure enough it was an anti-virus application that was causing the uninstall. Another customer case was due to user not having permissions to install apps.  See more details on installation troubleshooting.