Chad Butler on "[Plugin: WP-Members: Membership Framework] Error when activating plugin"

The places where this is failing are related to some of the plugin's stored settings that, based on the errors you have displayed, don't seem to be loaded properly.

Looking at the directory wp-members-master my question is where did you get the original install package? Was this downloaded from GitHub? And if so, what specific package?

If this was loaded directly from wordpress.org, generally, the directory is going to be /wp-members/.

The directory name itself doesn't really matter for the plugin to operate, but in trying to figure out why you don't seem to have a clean install it makes me question whether you've got something out of date (such as the BlueHost mirror at https://github.com/wp-plugins/wp-members which is severely out of date) or something beta (such as my repo here: https://github.com/butlerblog/wp-members/).

In either case, I think what you need to do is clear things out and reinstall. In order to make sure that reinstalling results in a clean install, you need to deactivate the plugin in the WP plugin panel, then run the delete option in the plugin panel to make sure that any db settings are removed. Then install the package from here on wordpress.org.