ChemDraw: Unable to launch ChemDraw 20.1 serial number prompt in the activation window.

Unable to launch ChemDraw 20.1 serial number prompt in the activation window.

When the software is installed on a flash drive or missing .dll files you will receive the activation prompt for our legacy versions that includes the serial number field. You need to make a clean installation on your local C: drive.
Please uninstall ChemOffice from the Control Panel Apps
Scroll down to letter P and remove all the previous versions of ChemDraw / ChemOffice

Then remove the following folders:
C:\ProgramData\PerkinElmerInformatics
C:\Program Files (x86)\PerkinElmerInformatics
C:\Program Files \PerkinElmerInformatics

If you can't see the ProgramData folder check this FAQ from Microsoft: -Hidden files 

Open the Registry Editor of your PC (Run regedit)

Delete the following folders
32-bit OS
HKEY_LOCAL_MACHINE\Software\PerkinElmerInformatics\
HKEY_CURRENT_USER\Software\PerkinElmerInformatics\

64-bit OS
HKEY_LOCAL_MACHINE\Software\PerkinElmerInformatics\
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\PerkinElmerInformatics\
HKEY_CURRENT_USER\SOFTWARE\PerkinElmerInformatics\

Try the installation of your software again, run the cos20.1.exe file by right-clicking on it and select Run as Administrator.