Enfold update

Hey Julien ,
Each license is only purchased once and has lifetime updates, the support for each license is only good for either 6 or 12 months depending on what was purchased.
If you purchased all of your client licenses in your Envato account, you would also need to purchase the support renewal for your clients in your account. Envato doesn’t allow transfer of licenses.
As for updates, if all licenses are from your account with your Token, then the client may need your help to update, expressly for older versions that are using the old Envato API, pre v5
They will first need to be manually updated, and then you can create a new Token for the client. You should be fine after that, unless Envato changes again in the future.
Also note that Envato has a daily limit on update checks, I believe that is 20, so after 20 checks you will need to wait 24 hours. If one client has an old version that has the old API and checks 20 times, all other of your licenses will not update.
You will probably need to review each site and manually update everyone to v7.1 and ensure that all Tokens are working, then going forward every thing should be fine.
Note that the Token needs specific permissions, the Envato Market plugin requires fewer permissions and might be better for you.
To manually update Enfold you will need to download the latest installable WP version from your Theme Forest account and upload it to your WordPress ▸ Appearance ▸ Themes ▸ Add Themes ▸ Add New

after you choose the zip file and click install, you will see a This theme is already installed message because you are updating, you can continue

then you will see the Theme updated successfully message.

I hope this helps.

Best regards,
Mike