Thank you for posting.
We do advise in the software that a new version is available, but it is also explicitly stated in a prompt that depending on your license, a license upgrade may be required.
With regards to the TeamViewer plan, there are two types of plans. One is perpetual license, another is subscription. You need to make sure which types of license you are holding.
If you have a subscription plan, you are able to use the latest version, such as version 14. However if you have a perpetual license, you need to use the version you purchased.
(1) If you are interested in a subscription,
Once you setup for an auto upgrade, you do not need to do anything.
Please read the below articles in order to enable to update.
(2)If you would like to keep using your perpetual license,
Please uninstall your current version of teamviewer and install the previous version from here. Also if you wants to avoid updating to the latest version automatically please see this article and make sure that you select "updates within this major version".
rather than having the end points download from our website, you can create a custom download link for the host (unattended access) or QuickSupport (attended access)
You can see how to do this here.
Hope this information will be helpful for you.