Did you get a pop up at any point from Windows’ UAC system that asked you if you wanted to run a particular program? If you went away during the verification, you may of missed this which would cause it to fail.
If that isn’t the problem, please navigate to C:\Program Files(x86)\Epic Games and then to either 4.11 or , whichever is newer (I’m assuming that they were installed at some point, if not, please let me know and I’ll let you know how to proceed from there) and then navigate to the Engine/Extras/Redist/en-us/ folder. There should be a UE4PrereqSetup_x86 file. Run that and you should have the option to Uninstall. Please do that and then try verifying again.