App download on iPhones

Ambassadors - Did anyone have issues downloading the ECHO app on an iPhone?

I was asked to use this link https://testflight.apple.com/join/dUF1Y7pD- open it on my phone. It should be a simple two step process: download the TestFlight app, open the TestFlight App, and then download the ECHO app.

One of my citizens have downloaded the TestFlight app but it’s asking them to put in a redeem code.

Does anyone know why it’s asking this and how to download the app without a code?