From 2014 to 2020, the iOS Project Builder for Unity was distributed in the form of an installer file located in the asset package. This has changed: by 2020/07, Unity strenghtened the Asset Store rules to forbid the inclusion of executables (which is understandable for security reasons), as a consequence I can no longer distribute the toolchain's installer in the asset itself.

In order to get your installer, please head up to: https://www.pmbaty.com/iosbuildenv/iosbuilder.php and enter your Unity invoice number. The website will generate your dowload and send you the URL where to download your registered version of the installer.

Thank you for your understanding.

						-- Pierre-Marie Baty


TL/DR:
 - Open https://www.pmbaty.com/iosbuildenv/iosbuilder.php, input Unity invoice no, download, install.