What is a permanent subscription and how is it supposed to work?

I have three 'Permanent' subscriptions logged in my account.
I was under the impression that these are automatically renewed and that I can use the same code for any new versions that come along.
Yesterday, I downloaded v13 of Parallels for Mac, upgraded, but it didn't allow me to use my existing code. Instead, I had no choice but to buy an upgrade subscription, but notice this is a new entry in my account that I don't think I needed.

Can a representative at Parallels explain?

 

Hello @boyplunder ,
Please refer http://kb.parallels.com/122929 to find the difference between 1-Time Purchase and a Subscription based license for Parallels Desktop.
On checking your records we found that you have 3 Parallels Desktop 12 permanent licenses (not subscription) which are non-renewable and you have one Parallels Desktop 13 Home edition (subscription, you would have received a new key to activate this copy ) which is valid until August 18'2018 and you have purchased Pro edition upgrade (subscription) on 25/09/2017 which can be used to upgrade any one of your Parallels Desktop 12 permanent license to version 13.

Thanks, Alfena

 

Hi Alfena,
Thank you for your response. Unfortunately, this doesn't quite answer my question.
The kb file doesn't explain it very well either. For instance, it doesn't mention 'Permanent' subscription, and I want to avoid any confusion here.
Ideally, I want to buy one subscription for each of the computers we have. It then renews each year, but I can use the same subscription and code for any upgrade. What subscription should I buy?

 

Hello @boyplunder ,

You can purchase the pro edition which is available as a subscription-based license and once you have renewed the subscription you can use the same license key to activate your copy.
Thanks