You may need to "deactivate" the old device in your account dashboard before the key will work on a new installation. Mitigating malware and ransomware attacks

: You can download the official Malwarebytes installer and get a 14-day trial of all Premium features—no credit card required.

: After the trial, the software reverts to a free "cleanup" version. It doesn't have real-time protection, but it is excellent for manually scanning and removing existing infections.

: Check the official Malwarebytes store for seasonal sales. Sometimes student or military discounts are available through verified platforms.

If you already own a legitimate "lifetime" key from years ago and are having trouble activating it in newer versions (like v4 or v5):