Hello and sorry for reopening this issue but I have it as well.
The problem is that Powershell has case-sensitive commands and pip is trying to call path completely in minor case

PS C:\Users\federico.Tabbo\git\nexus2aci\env\Scripts> .\Activate.ps1
(env) PS C:\Users\federico.Tabbo\git\nexus2aci\env\Scripts>
Fatal error in launcher: Unable to create process using '"c:\users\federico.tabbo\git\nexus2aci\env\scripts\python.exe"  "C:\Users\federico.Tabbo\git\nexus2aci\env\Scripts\pip.exe" ': The system cannot find the file specified.


if I run the lowercase path I get an error

(env) PS C:\Users\federico.Tabbo\git\nexus2aci\env\Scripts> c:\users\federico.tabbo\git\nexus2aci\env\scripts\python.exe

c:\users\federico.tabbo\git\nexus2aci\env\scripts\python.exe : The term
'c:\users\federico.tabbo\git\nexus2aci\env\scripts\python.exe' is not recognized as the name of a cmdlet, function,
script file, or operable program. Check the spelling of the name, or if a path was included, verify that the path is
correct and try again.
At line:1 char:1
+ c:\users\federico.tabbo\git\nexus2aci\env\scripts\python.exe
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : ObjectNotFound: (c:\users\federi...ipts\python.exe:String) [], CommandNotFoundException
    + FullyQualifiedErrorId : CommandNotFoundException


Running the correct case path works

(env) PS C:\Users\federico.Tabbo\git\nexus2aci\env\Scripts> c:\Users\federico.Tabbo\git\nexus2aci\env\Scripts\python.exe

Python 3.8.4rc1 (tags/v3.8.4rc1:6c38841, Jun 30 2020, 15:17:30) [MSC v.1924 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
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