Confirmation letters are sends immediately after click the icon. Letters to icloud domain come with a delay 10-20 minutes.
Also please check all folders, including the spam folder. If the mail doesn't arrive, there is probably no space in your mailbox to receive the letters. Clean up your mail. Also check if your google photo backup or icloud photo backup is taking up space in your mail.
After free up your e-mail, you can try to create a new withdrawal and confirm it by the confirmation letter.
In rare cases it might happen that a letter arrived at your email, but didn't show up in your mobile app in time. In this case, we recommend to check your mail through your browser.
If the letters do not arrive even after clicking the re-send button, contact [email protected]