A common issue for pc's that have not had Flex installed on them before, is when the admin installs client and receives errors that the client is unable to be installed. This is commonly being seen on new Windows 11 machines. Sometimes the errors are different, but the resolution is the same. Here are two examples below. 

a.Press Windows key + X and select Command Prompt(Admin).
b. At the command prompt, type the commands mentioned below and press Enter after each command-
regsvr32 ntdll.dll /s
regsvr32 msdxm.ocx /s
regsvr32 dxmasf.dll /s
regsvr32 wmp.dll /s
regsvr32 wmpdxm.dll /s
c. After registering DLL files restart the computer 

d. Proceed to install the client