Since it was released in June, I’ve installed Exchange 2016 Cumulative Update 2 (CU2) a few times. After the past 2 installs, I’ve had issues connecting to the admin center and OWA and greeted with a “500 – Internal server error”.
In both cases, I could not find a simple resolution and needed to re-install Exchange (from the command prompt)…
Setup.exe /Mode:Upgrade /IAcceptExchangeServerLicenseTerms
Good luck and have fun!