License Key doesn't work for Scrivener 2.6

Hi, I’ve just purchased a license key but it’s obviously only for Scrivener 3. I need to keep Scrivener 2.6 because I have an old Mac with operating system 10.11.6. I’m attaching a screenshot of the message I get when I try to register with my email address and the license key. Sorry, it’s in Spanish but it says that either email or license key are not valid or don’t match. What can I do? I downloaded Scrivener 2.6 ages ago but only started to use it regularly two weeks ago. Now my trial version is about to expire and I’ve already started to work on a project. I also sent a message to the support but received an email that an answer may take several days.

Will version 2.9 not work for your system? It works for all Intel-based macs from version 10.9 through 10.12, and should accept your license key (or it may not require one anymore, due to a recent change in which company handles their license verifications).