ngx_pagespeed admin statistics don't load

I followed the official install guide to build nginx with the latest stable pagespeed module. It works in some regards so I'd like to debug further with the admin tools. They are enabled in nginx as follows;

http {
    pagespeed FileCachePath "/mnt/ramdisk/ngx_pagespeed_cache";
    pagespeed StatisticsPath /ngx_pagespeed_statistics;
    pagespeed GlobalStatisticsPath /ngx_pagespeed_global_statistics;
    pagespeed MessagesPath /ngx_pagespeed_message;
    pagespeed ConsolePath /pagespeed_console;
    pagespeed AdminPath /pagespeed_admin;
    pagespeed GlobalAdminPath /pagespeed_global_admin;
}

server {
    location /ngx_pagespeed_statistics { allow 12.34.56.78; deny all; }
    location /ngx_pagespeed_global_statistics { allow 12.34.56.78; deny all; }
    location /ngx_pagespeed_message { allow 12.34.56.78; deny all; }
    location /pagespeed_console { allow 12.34.56.78; deny all; }
    location ~ ^/pagespeed_admin { allow 12.34.56.78; deny all; }
    location ~ ^/pagespeed_global_admin { allow 12.34.56.78; deny all; }

    pagespeed on;

    location ~ "\.pagespeed\.([a-z]\.)?[a-z]{2}\.[^.]{10}\.[^.]+" {
        add_header "" "";
    }
    location ~ "^/pagespeed_static/" { }
    location ~ "^/ngx_pagespeed_beacon$" { }
}

(Where 12.34.56.78 is my IP address)

When I visit https://example.org/ngx_pagespeed_statistics I see a brief glimpse of statistics before it says "Sorry, failed to update the statistics. Please wait and try again later."

In the browser inspector I see it tries to load /ngx_pagespeed_statistics/stats_json which returns a 404.

Did I miss a step in configuration? What could be the cause?