The issue here is server related. I took a copy of your site and was able to see the custom fields on my end without any issues.
However I did check the debug data for your site and saw that you're running MYSQL version 5.5 . The minimum version required for Toolset is version 5.6 so I would advise that you contact your host for them to update the mysql version.
Furthermore it would be best to take a look at our minimum server requirements at the link below and ensure that your server meets these. https://toolset.com/toolset-requirements/