There are clearly still issues around the ability to index/search the pypi projects list. We aren’t currently sure why these issues only affect some machines, but we are working on a fix so that you can still install the plugins (psychopy packages that are known to us) can be installed as well as any packages that you know the names of.
Workaround: If you already know the name of the name of the package you want then the current workaround is to do this from PsychoPy’s Python shell (the Shell panel in the Coder view):
>>> from psychopy.tools import pkgtools
>>> pkgtools.installPackage( 'name-of-my-package' )