I just don't think it's fair that I can's use the addons I've paid for. Your terms and conditions only stipulate that payment ensures updates, they don't say that I won't be able to use them at all after the year I've paid for. You need to update your terms and conditions to say that all addons will be deactivated after the payment period. I've never heard of any premium Wordpress plugin that disables itself, they usually just discontinue updates after the payment term runs out. but they are still useable.

@angeljs,

Please read my second reply. You do can use your addons lifetime until the become incompatible with some version. I've already said above that you do can use it. The license key is only for getting updates, it doesn't stop addon working. Your addons work with 5.3.5 version fine, just continue using them. You don't need to activate the license. Just forget about the license activation and continue to use your addons. Again, the license activation is only needed to get new version updates as the license agreement says and as you can see on your screenshot text.

So just ignore the activation request in the settings page and continue using your addons. but make sure you're using wpDiscuz 5.3.5 version. Because the addons you have is compatible till the 5.3.5 version.

I purchased the developer license, but can't use it as I can't access the keys, even for the older versions. Do you mean I have to keep paying to even use the addons that I have purchased? I thought payment was just for future updates?

@angeljs,

Let's start from the beginning again. As you already know your license keys are expired. It doesn't matter what wpDiscuz version you use. The license keys are expired and you cannot activate them. Could you please read my second reply again? https://gvectors.com/forum/product-license-questions/where-are-my-license-keys/#post-23686

All plugins and addons updated automatically, how do I downgrade? 

Ok, please deactivate wpDiscuz plugin, then delete it in Dashboard > Plugins admin page. You don't need to delete addons, just keep addons deactivated.

Then download the attached previous 5.3.5 version of wpDiscuz, go to Dashboard > Plugins > Add Plugin admin page and upload/install/activate the zip file. Then activate all addons.

Yes, I know all of that, but the addons have all disabled themselves in my site and are asking for a key. 

Yes, if you've updated to wpDiscuz 7 your addons will be automatically disabled, because they are not compatible with wpDiscuz 7. I've already mentioned above that you should only use 7.x.x versions of addons with the current 7.0.2 version of wpDiscuz.