When you still have licenses available, but are getting the following error when trying to activate "You are attempting to exceed the number of clients permitted to use your license. You should purchase an additional license or release a license copy being counted by license checks on other PCs."
This error usually happens (when licenses are still valid) when a user is trying to access the program remotely or install the software on a virtual desktop without a TSL (Terminal Server License) SN.
A TSL (Terminal Server License) is required in order for the software to work under such environments. Please refer to the below for more details or contact firstname.lastname@example.org.