I am finding the same problem when I open your site in mobile view. It even happens when I use safe-mode to open the site.
The errors I’m seeing in the console are:
GET https://community.bcro.org/categories.json 500
Error while processing route: discovery.categories
When I open the site in the desktop view, there are no errors on the categories page.
You can load the mobile view of your site on a desktop by going to https://community.bcro.org/?mobile_view=1. If you do this, and open your site’s error log page (Admin / Logs / Error Logs), you should see an error message that will give more details about what is going wrong. To filter the logs, deselect the Debug, Info, and Warning checkboxes from the bottom left of your logs page.
Let us know what you find in the logs.