Many websites repost old giveaway keys from 2015 or 2016. Remouse developers have blacklisted these keys long ago. If you enter a key you found on a forum, the software will likely display: "Invalid License Key" or "License has been revoked."
Even legitimate users run into issues. Here is a quick troubleshooting guide: Remouse Standard License Key
Issue 1: "Invalid key" error.
Issue 2: "Key has been blacklisted."
Issue 3: Lost my key after reinstalling Windows. Many websites repost old giveaway keys from 2015 or 2016
Once you have your legal key, activation takes less than 30 seconds: Issue 2: "Key has been blacklisted