When upgrading a Delivery Controller to version 7.16, a Citrix licensing error message might appear "One or more issues were detected with your licensing configuration. If unresolved, such issues will affect users' ability to access applications and desktops after the site upgrade"

Verify that you have valid XenApp/XenDesktop licenses installed prior to upgrade, and that the SA date is 2017.1115 or newer. You can view this on the license server by logging on to the Citrix licensing administration console. If not, make sure you upgrade your CSS/SA or download and install renewal licenses on the license server. How to Download and Install Updated License Files after a renewal

Also, make sure that your License Server is version 11.14.01 (any build number) 

If all licensing is in order, you can safely check the box next to Let me continue, and click Next.

One or more issues were detected with your licensing configuration. If unresolved, such issues will affect users' ability to access applications and desktops after the site upgrade