ERROR: HTTP error 404

/home/pi/oprint/bin/python2 -m pip --disable-pip-version-check install pop ive/ --no-cache-dir
ERROR: HTTP error 404 while getting pop ive/
ERROR: Could not install requirement

You're link posted here seems to have an errant 'pop' inside 'archive' in the url?? And some more details about what you were trying to do would be nice. This works for me:

Update window come up, hit apply and I get this error.

Update Available

There are updates available for the following components:

Those components marked with can be updated directly.

try to run it and I get an error

The update did not finish successfully. Please consult octoprint.log and plugin_softwareupdate_console.log for details.

How about posting the logs... octoprint.log and plugin_softwareupdate_console.log seeing as OctoPrint is telling you to look there?