the switch itself needs Networking Essentials or Networking Advantage license
smart licensing is intended to keep your infrastructure operational even if licenses have expired
it will complain by logging messages (lots of it), but remain operational, it will give you plenty of time to renew the license
so I agree with @Flavio Miranda it is very strange your switch stopped working there probably was another cause that happened on the same time
"you generated a new one" ??? what do you mean by that, did you request a new license in the Cisco portal?
Cisco DNA center is the successor of Cisco Prime Infrastructure as Cisco Prime Infrastructure was the successor of Cisco NMS
to manage the switch using Cisco Prime Infrastructure server you need the Prime Licenses
to manage the switch using Cisco DNA center you need the Cisco DNA center Licenses (Essentials or Advantage)
the switches' model (C9300, C3560CX) is included in the license name
Cisco DNA center can use additional functions, like ThousandEye? StealthWatch (and needs those licenses)
look at this document how licenses enable features on switch and DNA center
Enterprise Networks Software Subscription Matrix for Switching - Cisco
if you do not use Cisco Prime Infrastructure server you can ignore the Prime licenses,
they are supplied as "courtesy" for clients migrating from Cisco NMS to Cisco Prime
if you do not use Cisco DNA center, you can ignore the DNA licenses including ThousandEyeand StealthWatch
Cisco ISE is an authentication server that uses licenses by this name,
Plus unlocks more features than Base just like Essentials and Advantage
look at this document:
Cisco ISE Licensing Guide - Cisco chapter 3.1
if you do not use Cisco ISE you can ignore the ISE licenses
I'm not sure how Cisco ISE behaves if these license expire?
if you DO use Cisco ISE and this servers stops authenticating , that may have been the problem.
the switch remains operational, but client authentication is not validated by ISE (DOT1x) then clients are not granted access to the network
