That is a Windows install / uninstall issue and not eM Client.
Running the Microsoft Troubleshooting program below up to Windows 10 normally fixes that.
Failing that you have more of a Registry issue and need to contact Microsoft for further help.
Fix problems that block programs from being installed or removed (microsoft.com)
there are no links to previous installers on the eM Client website
Release History All versions for PC up to now latest V9 | eM Client