Having issues setting up EMclient for the first time using an Icloud account.
I am using the app specific password from my apple ID but the setup still fails.
I can only suggest to try “removing your previously generated app password” in your Apple account, and then “regenerate a new Apple iCloud app password” as per the following Apple webpage below.
Could be the app password you used with eM Client might have eg: “been possibly used with another device” or “had a typo in some way”. Each app has to have its own generated password.
(Sign in to apps with your Apple Account using app-specific passwords)
https://support.apple.com/en-au/102654
(eM Client with iCloud)
https://www.emclient.com/em-with-icloud
If it still fails with a brand new generated app password, then update what version of eM Client you are using and also if you have Windows or Mac and your OS version.