The GFW uses a few different methods of blocking, but the most common is by blacklisting IP addresses. If your content is not something specifically disapproved by the censors, then you may be on an address or in a netblock that was blocked previously. Changing your IP or hosting may help.
If you don’t have HTTPS enabled, then do so, as that will bypass the naive keyword blocking that sometimes happens. Also, do you use a CDN for assets? Many are heavily throttled or outright denied. Enabling Google Analytics is another possible cause.