503 Error

WordPress version: 4.6
Plugin version: 1.7.6
Link to my site: http://jsewers.co.nz/demo-new-page/

I expected the plugin to do this:
Calatloge was displaying fine

Instead it did this:
On content update, 503 service unavailable error arises

Here’s what I’ve tried so far:
Removed shortcode for WP Cataloge and page loads fine.
Tried on new page and it produces same error.