To stop Supercell ID from asking you the verification code every time you want to log in, be sure to tick the box for "Remember me on this device."
If you are playing several accounts, you get the best experience when you attach all your game accounts to Supercell ID. This way, you can switch between all of your accounts without entering verification codes.
The "Remember me on this device" tick box is under the field where you enter your email address.
Only a valid email address can be used for the creation of a Supercell ID because logging in requires being able to retrieve a verification code from this address.
If you haven't received the verification code, please check your spam folder and double-check that you have no rules set in place that might make these emails end up in a folder. Searching your inbox with “Supercell ID” should find the emails with the verification code.
Please note that only the very latest verification code sent to you will work.
Please note that for each login and creation, you will be sent a new verification code, and only the newest verification code will work.
Make sure you know which verification code email in your inbox is the latest one. If you already have several Supercell ID verification codes in your inbox, delete them all and start the login/creation process again in the game.
Please note that when you sign up for a Supercell ID, you have to provide a valid email address that you can access. If you suspect that your email provider might not be supported, please try signing up with another email address.