Hi, you are using a debug build of the app with your live account settings.
You need a release build of the app instead (just use the build from https://certifytheweb.com) or you can set the email address under ‘Settings’ again which will switch you to a Staging account (i.e. test, you cannot use the Let’s Encrypt staging api for real certificates).
If you did not build the app yourself and you are not using the official release you should use extreme caution and check for malware, then switch to the official build.