Hello. My activation key is not working for the version of Parallels I am trying to use, and I need assistance. I am trying to use Parallels to virtualize an older Mac that is on OS X Yosemite. For this, reason I downloaded Parallels Desktop 13, the latest version that supports Yosemite (https://kb.parallels.com/114381). The trial period was over so from the app, I clicked to "Buy." It redirected me to https://www.parallels.com/products/...d_activation&status=non_activated&signed_in=1 , where I then purchased Parallels Desktop Standard Edition (Cleverbridge# 280624247). But when I enter the activation code it gave me, it says "Unable to perform the operation. The license server rejects it." I believe that the license I bought is for Parallels Desktop 16 for Mac, the current latest version of Parallels, and the activation code is not letting me register Parallels Desktop 13. (According to https://forum.parallels.com/threads/license-server-rejects-it.353575/#post-886441: "We see that you have purchased a one-time key for Parallels Desktop 16 which cannot be used to activate Parallels Desktop 14. If you buy a yearly subscription key, that can be only used to activate Parallels Desktop 14.") I would expect that the "Buy" option from the application I am using would let me buy FOR THAT APPLICATION. But the option to purchase a Parallels 13 key wasn't given to me when I purchased the key, nor was there information stating that only a yearly subscriptions can activate older versions. If a subscription is what is necessary to run the older version that supports Yosemite, then I ask that we switch my "1-Time Purchase" to the "1-Year Subscription." I also ask that Parallels improves their information/documentation (such as on the legacy version page and during the purchase process), so these kind of scenarios and mix-ups don't happen to anyone else. I look forward to your response and assistance. Thank you. -Matt Hallaron p.s. I also communicated this in Facebook Messenger, where I await a response. I apologize for the repetition.