I'll accept your apology for the inconvenience. I spent a lot of time trying to resolve my issue of not being able to post remotely with one of my remote posting programs.
It didn't occur to me that Wordfence may have been causing the issue or I would have come to this support forum first.
After hours upon hours of frustration of trying to figure it out myself I asked the tech support from my VPS host to look into my issue for me.
Wordfence is the only plugin that shows such a recent modification time. I recommend disabling the Wordfence plugin and attempting to make another post via the XMLRPC API. If the post works with this plugin disabled, then we can safely assume Wordfence is causing the problem.
All is well that ends well. I came here to determine if I would need to delete Wordfence completely until the issue was resolved and I'm happy to see it is as simple as unticking an option.