As soon as you create an account, you'll receive an email with an account activation link.
In case you haven't received the email, please, check your spam or junk folder. If you have several email addresses make sure you signed up with the email you're checking. If you still don't see it, you need to send an activation request to MuseScore Support at support@musescore.com or https://musescore.com/contact and send us proof that you are the owner of the account, such as a receipt of purchase.
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