When I try to install plotly with pip in a Mac with python 2.7, i get the following message:
Could not fetch URL https://pypi.python.org/simple/plotly/: There was a problem confirming the ssl certificate: [SSL: TLSV1_ALERT_PROTOCOL_VERSION] tlsv1 alert protocol version (_ssl.c:661) - skipping
Could not find a version that satisfies the requirement plotly (from versions: )
No matching distribution found for plotly
Are you using Anaconda by any chance? If so, have you tried installing using Conda?
I’m not very familiar with pip’s internals, but it sounds like you may be running into this issue: https://github.com/pypa/pip/issues/5226.
If so, sounds like you need to get pip updated to at least 9.0.3
So I would suggest using that issue thread as a starting point for diagnosing the issue.
Hope that helps get you pointed in the right direction.