How do I activate the license key in FTS 4.0?

If you are having issues activating the FTS paid extension(s) license key, please note that as long as both the free FTS plugin and the paid FTS extensions are both installed and active, the plugins will function fine despite the license key not taking.

While the plugins will still function without the license key installed and/or a warning message, here's a link to help you to install & activate your license key: https://www.slickremix.com/documentation/activating-extension-license-key/