The title says it all. I have contacted my hosting company and they are clear this is not their issue.
I see from a support post that I may not be the only one having this problem. I have Deactivated my other plugins and tried to search Plugins but the same error message comes up.
When I go to Add New in the Plugins, the page reads: "An unexpected error occurred. Something may be wrong with WordPress.org or this server’s configuration. If you continue to have problems, please try the support forums."