If you did not download the key file when you created the account, and you cannot remember your password, your data is irretrievable. Mega cannot reset your password without the key because doing so would decrypt your data, violating their privacy policy. In this scenario, you can reset your password to regain access to the account (the empty shell), but all previous files will be permanently encrypted and inaccessible. They will appear as gibberish data.
: To prevent water damage or fading over time, place the paper in a plastic sleeve or laminate it. Secure Storage Mega Recovery Key Txt File Download
Tap Menu (bottom right) > your email address > Back up recovery key > Save . Key Details to Remember If you did not download the key file