I've been trying to get the 30 day trial to work for the latest Start 11. (I can't say exactly which version because it won't let me past the little trial activation popup window over the main window, but I downloaded it from here tonight, so....) However, I've tried to click on the Activate button in my email from two different browsers (Librewolf and Opera GX), and am getting the same error regardless:
The resource cannot be found.
Description: HTTP 404. The resource you are looking for (or one of its dependencies) could have been removed, had its name changed, or is temporarily unavailable. Please review the following URL and make sure that it is spelled correctly.
Requested URL:/sas/2014-02-01/validation/validate/MTIwMTIwMDU0fG9ueXhkcmFnb25zdHVkaW9AZ21haWwuY29tfG95di95cEV0TzFQTTFpUWVPNTF3L25BdTFXall0Vm4rZkY0M3RoQ0kyTUJidFBFazAwM0hpZz09fDI2NzR8U3RhcnQxMSB2MnxGYWxzZXxUcmlhbA==
Both browsers are up to date, but that's honestly irrelevant. A 404 error like this shows up literally only when there is not the expected resource. It looks like an upgrade happened and the software wasn't reconfigured properly to automatically generate the necessary URL in the emails.
Also, I didn't post the info here, but whoever is running your IT backend needs to change the 404 message. The above is great troubleshooting, but the .NET framework and the ASP.NET versions are listed on that page too. That's literally ***begging*** for a hack across whatever problems are known to exist on those versions of the software.