I never got around to posting this request/issue so I've actually had the plugin disabled for quite some time. It would seem that this plug hooks in such a way that it prevents being able to authenticate and ultimately post via XMLRPC and/or the WordPress Mobile Apps. I'm not quite certain if the WordPress Mobile Apps are using XMLRPC or not but I do know that when I have this enabled on my account I lose the ability to access from the mobile app. I'll be honest that I'm not sure if there is actually a fix for this. It doesn't seem that the mobile app has any way to know what plugins are installed in a WP site and have any way of presenting that functionality in the mobile app. The solution would be to not require the OTP when accessing via Mobile App or XMLRPC but then it really wouldn't be providing much security then anyways. However I wonder if there wouldn't be some way of including the OTP as a part of the password. Though I'm not certain this would be of use as I cannot plug my Yubikey into my Android phone. Well, as I've said I don't really have any good solutions off the top of my head but I thought that I'd at least report it in the hopes that someone has a great idea. I love the idea of using my Yubikey to secure the WP sites, it's just not practical from a Mobile Admin perspective.