Cannot install version 1.0.9

[Rod-in-NM]

We're having difficulties installing version 1.0.9 into a WPF app. This is the list of steps fed to VS 2019's Output window:

Attempting to gather dependency information for package 'ModernUI.WPF.1.0.9' with respect to project 'PharmacyWarehouse', targeting '.NETFramework,Version=v4.5.2'
Gathering dependency information took 68 ms
Attempting to resolve dependencies for package 'ModernUI.WPF.1.0.9' with DependencyBehavior 'Lowest'
Resolving dependency information took 0 ms
Resolving actions to install package 'ModernUI.WPF.1.0.9'
Resolved actions to install package 'ModernUI.WPF.1.0.9'
Adding package 'ModernUI.WPF.1.0.9' to folder 'C:\Src\PharmacyWarehouse\Pharmacy Warehouse\PharmacyWarehouse\packages'
Install failed. Rolling back...
Package 'ModernUI.WPF.1.0.9' does not exist in project 'PharmacyWarehouse'
Removing package 'ModernUI.WPF.1.0.9' from folder 'C:\Src\PharmacyWarehouse\Pharmacy Warehouse\PharmacyWarehouse\packages'
TF400024: The change on C:\Src\PharmacyWarehouse\Pharmacy Warehouse\PharmacyWarehouse\packages\ModernUI.WPF.1.0.9\ModernUI.WPF.1.0.9.nupkg cannot be undone because a file already exists at C:\Src\PharmacyWarehouse\Pharmacy Warehouse\PharmacyWarehouse\packages\ModernUI.WPF.1.0.9\ModernUI.WPF.1.0.9.nupkg. The file must be deleted from disk for the undo to succeed.
Time Elapsed: 00:01:22.2454264
========== Finished ==========

Note, it complains that the package can't be installed, then it tries to uninstall it, but that fails "... because a file already exists at C:\Src\PharmacyWarehouse\Pharmacy Warehouse\PharmacyWarehouse\packages\ModernUI.WPF.1.0.9\ModernUI.WPF.1.0.9.nupkg". That makes no sense because I made sure the ModernUI.WPF.1.0.9 folder doesn't exist under the packages folder before starting. So, it's the process of trying to install ModernUI 1.0.9 that's putting whatever file its complaining needs to be deleted.