After upgrading Delivery controllers from 1912 to 2402, unable to view license usage in Studio. 

Studio show error : An error has occurred with the Citrix License Server. Check the license server to make sure it is running, then try again

1. Take the Delivery Controller backup.
2. Uninstall Microsoft Visual C++ 2015-2022 Redistributable (x64) and Microsoft Visual C++ 2015-2022 Redistributable (x86)
3. Reboot Delivery Controller.
4.  Install the Microsoft Visual C++ from ISO ( E:\Support\VcRedist\ Where E: is the drive letter for ISO mount)

Problem Cause

Corrupt  Microsoft Visual C++ Redistributable tools