If you have an issue installing Nintex Workflow & Nintex Live on your server.
The installer completed successfully, but there were errors in the Event Viewer when starting the service from Central Admin. After talking to Nintex support, they mentioned that there should have been a windows service "Nintex Live Relay Service". But it was not listed.
So re-install Nintex, and when it is complete, look at the logs hoping to see more information about the service.
Luckily, its location is listed, so use installutil.exe to manually install it.
Open command prompt, run as Admin:
installutil "C:\Program Files\Common Files\microsoft shared\Web Server Extensions\15\BIN\NintexLive\Nintex.Live.RelayService.exe"
Go in Central Admin, System Settings, Manage Services on Server, and start Nintex Live Relay service.
This document was generated from the following discussion: Nintex Live Relay Service-how to manually install
This worked from me for the External Relay Service and I didn't have to install Nintex again. We are using SharePoint 2016 OnPrem.
I logged on to the server and ran the following in PowerShell: