Error installing plugin - Exclude Region

What is the problem?

I'm getting an error trying to install the plugin via the command line.

What did you already try to solve it?

The command line, the URL, and the search bar (it won't click on the install button)

Complete Logs

octoprint.log, serial.log or output on terminal tab at a minimum, browser error console if UI issue ... no logs, no support! Not log excerpts, complete logs.)

Using cached
ERROR: Command errored out with exit status -1:
command: 'c:\python27\python.exe' -c 'import sys, setuptools, tokenize; sys.argv[0] = '"'"'c:\users\mb\appdata\local\temp\pip-req-build-j1zz9r\'"'"'; file='"'"'c:\users\mb\appdata\local\temp\pip-req-build-j1zz9r\'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(file);'"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, file, '"'"'exec'"'"'))' egg_info --egg-base 'c:\users\mb\appdata\local\temp\pip-pip-egg-info-c4b_r4'
cwd: c:\users\mb\appdata\local\temp\pip-req-build-j1zz9r
Complete output (1 lines):
Could not import OctoPrint's setuptools, are you sure you are running that under the same python installation that OctoPrint is installed under?
ERROR: Command errored out with exit status -1: python egg_info Check the logs for full command output.

Additional information about your setup

OctoPrint version, OctoPi version, printer, firmware, browser, operating system, ... as much data as possible

Octoprint v3, running on Win10 in google chrome.
I'm also running two printers in two different tabs. I made a copy of octoprint and named it octoprint2 and assigned it the port 5001. But the application is named octoprint in both folders.

I am sorry, there is no OctoPrint v3. There is Python 3. But there are many different versions of Python 3, and not all of them are compatible with OctoPrint (you need Python 3.6.0 or newer). Only OctoPrint versions 1.4.0 and later are compatible with Python 3.

A full OctoPrint.log (as requested in the issue template) would have told us what versions of Python and OctoPrint you are using.