Custom wordpress plugin fixes

We got a Wordpress plugin created by a freelancer and this very important project was left incomplete. -------New Request----- The plugin was once in working order. I assume that things only need to be "reconnected". Here are some of the things that are not working or were integrated poorly on our site: 1. Inbox functions (reply, delete, download, play button, etc.) not working but once were. 2. The MP3s play on the backend, but not on the front-end. 3. Mp3s, when downloaded, downloads an empty Mp3 file. 4. We want the general Wordpress login and the Partner Center login to be consolidated into one universal/global login. 5. Security is important to us, we want to ensure that member data (inbox and mp3s recordings) is not accessible to the public.