I am having the same issue – it stopped working when updating to 3.8.
i can’t even activate in wordpress 3.8
it redirects me to site domain
I am actually having the same issue with 3.71, and on different hosts… suddenly the wordpress smtp plugin stopped working (after working just fine) on several hosts for no reason. even when no other plugins are installed. I have no solution yet and have worked with the hosting support to try to figure out what is going on and so far no solution.
Found the issue to be Login Security Solution not allowing the update server to push the file to the local server.
I have the issue with no other plugins active and default themes (any of the twenty-X themes)…
Its not working on my site also after updating to wordpress 3.8..
Has anyone found a fix ?