I've checked with both engineering and QA.
This issue has not been observed before. It appears that the required registry entry for Expressor is not in the registry.
After uninstalling, be certain that the Expressor installatin directory is empty. Then try reinstalling and confirm that the registry entry exists.
On a 64 bit operating system, the registry entries will be at HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\expressor-software\studio\3.8.3
On a 32 bit operating system, Wow6432Node will not be in the path to the registry location.