Hi,
I’m guessing you’re using Mapbox. Mapbox will return empty tiles if your token isn’t authorized or if there’s another problem on their end (billing, etc.).
Do you have a URL where I can see the error? Or if you can provide a login to a staging site with the same problem, I can look there.
Where are you getting an AJAX error? The contact form on the site here seems to work for me. If you’d like to send a URL or login, please use that instead of posting here.