To update you app to the newest version, you have to completely uninstall the current LC app and download it again from the App Store:

LED line® LC controllers were deleted from our offer in 2020. Due to the responsibility towards users of the LC controller model purchased from our Distributors, we decided to continue the app support for at least a warranty time.

The application serves as a mobile remote control for the LED line® LC lighting controller.

With which you can control any strip from the LED line® offer. The device can operate in four operating modes as a dimmer for single-colour LED line® strips, MULTI WHITE, RGB and RGBW supplied with 12V to 24V voltage.

Updating the app may require you to pair the controllers again.