A few more notes...
1. Turning off Search Engine Friendly URLs in Joomla global config allows login
2. Our site is running JomSocial 4.5 (latest version)
I am having the same issue after updating to 3.8.4
Awesome! Thanks for the quick reply Melissa.
Users are getting the following error when attempting to use Twitter authentication...
error setting certificate verify locations: CAfile: /SERVER ROOT/libraries/joomla/http/transport/cacert.pem CApath: none
It looks like the cacert.pem file has been moved in 3.8.0, at least according to this tracker item... https://issues.joomla.org/tracker/joomla-cms/18004