Please try these steps instead with installing new build:
1. Clear the content of the directory under C:\users\your_username\Appdata\local\temp. For whatever reason, not all temp files automatically remove themselves and is NOT usually caused by Nitro Pro files.
2. Download and run our Clean Up utility to uninstall your Nitro Pro: http://install.nitropdf.com/support/downloads/cleanup.zip
NOTE: This clean-up tool will erase any existing signature files within Nitro so please save them to another location before using the clean-up tool in order to keep them. Please see this link for backing up custom stamps/signatures: http://kb.gonitro.com/knowledgebase#/search/stamps/000001686
3. Extract the utility to the desktop (it doesn't always run from the zip)
4. Run the utility then reboot your machine.
5. Now manually check for left over registries from Nitro Pro (Run > regedit) and delete them. Make sure to save a backup before making any change. Reboot the machine again after deleting Nitro Pro traces.
6. Please clear all your downloads folder or delete all downloaded Nitro installers. This step is important because we noticed that if you are saving all the installers and you download them in the same folder (like the downloads folder), the EXE can pick up any MSI installed in that folder and you may pick-up one of the older builds instead of the newly downloaded package.
7. Download and install Nitro Pro 18.104.22.1685 using offline installers:
If you are not sure which to pick, this will help: http://kb.gonitro.com/knowledgebase#/search/64/000001874
8. After installation, you can activate by opening Nitro, clicking on the Help tab > About Nitro Pro > Activation and entering your serial number.
These exact steps should be taken when installing Nitro Pro produces error "Nitro Setup Wizard has failed"