First time install of Relay Mac Recorder:
If this is the first time installing Relay before and you are installing it on High Sierra, due to the kext security changes, you will need to follow the step below:
1) Download the Relay Mac Recorder, and run the installation for Relay Mac Recorder.
2) When prompted with the message below, you will need to go to System Preferences > Security and Privacy > General.
3) Allow TechSmith Corporation Kext to load.
4) Finish the current installation.
5) After the first installation is complete, re-download/ reinstall Relay Recorder using the same steps.
6) Restart the computer.
You should have the Relay app listed in your Applications folder, after these steps.
Installing when Relay previously was installed:
If you had installed Relay Mac Recorder at one point, or you currently have the Relay installed, you do not need to follow the steps outlined above.
You should be able to install Relay using the prompts outlined in the installer.