Within a Command Prompt or PowerShell windows, run the following commands to being the uninstallation of Ninja
cd '.\Program Files (x86)' .\NinjaRMMAgent.exe -disableUninstallProtection .\uninstall.exe --mode unattended
Once completed, remove the existing Ninja Installation folder by selecting the folder and hold Shift+Delete to remove all contents.
Ninja can be reinstalled once the folder is removed. No reboot is necessary.
Attached is a script which will perform the same function, however some arguments will need to be added.
.\NewAgentRemoval_2022.ps1 -Uninstall .\NewAgentRemoval_2022.ps1 -CleanUp
Once the above arguments are processed, Ninja can be reinstalled again.