I’ve been working with my host, A2 Hosting, and after trouble shooting for a while we agree that it’s an issue with the theme. Here’s what they had to say:
Thank you for your reply and the information you provided. I was able to log in and see the issue with the “customize” function you are reporting, I was able to load the twentyseventeen theme and the customize options were all present. It looks like this may be an issue with that specific theme, there may be permission missing or some other issue that is preventing the theme from loading and being able to be customized.
I checked the debug changes you have made in the wp-config.php file and corrected them to enable debug logging. I am not sure this is an issue with the WordPress itself so there may not be errors to be reported.
I would recommend contacting the theme’s creator and letting them know you are unable to customize the theme, but are able to customize other themes and see if there is a setting or change that needs to be made to enable this.