Apache reserve proxy sends blank page

I'm now running Apache (2.4.38-3+deb10u4) on a Raspberry Pi (Raspbian GNU/Linux 10 (buster)). And it serves my webpages fine. It runs on port 443.

I have a service runs on port 4443 (/aghome in the configuration file), and when I try to use its reserve proxy to show this stuff, it shows me a blank page. But the other things I show with proxy works fine (/jsonrpc and /dns-query in the configuration file).

Seems like it's a page with just a JavaScript file.

The source code of the webpage.

And in the console, there are some errors.

The error information in the console.

When I open F12 developer tools, I can see the source code of the webpage, but it just doesn't work.

My Apache2 configuration file (/etc/apache2/sites-enabled/default-ssl.conf):

<IfModule mod_ssl.c>
    <VirtualHost _default_:443>
        ServerAdmin webmaster@localhost
        ServerName my-domain
        DocumentRoot /mnt/ks/www/html

        Protocols h2 http:/1.1

        ErrorLog ${APACHE_LOG_DIR}/error.log
        CustomLog ${APACHE_LOG_DIR}/access.log combined

        ProxyPreserveHost On
        ProxyVia On
        ProxyRequests Off 
        SSLProxyEngine On

        ProxyPass /dns-query https://localhost:4443/dns-query
        ProxyPassReverse /dns-query https://localhost:4443/dns-query

        ProxyPass /aghome https://localhost:4443/
        ProxyPassReverse /aghome https://localhost:4443/

        ProxyPass /jsonrpc https://localhost:6800/jsonrpc
        ProxyPassReverse /jsonrpc https://localhost:6800/jsonrpc

        SSLEngine on

        SSLCertificateFile  /etc/letsencrypt/live/my-domain/fullchain.pem
        SSLCertificateKeyFile /etc/letsencrypt/live/my-domain/privkey.pem

        <FilesMatch "\.(cgi|shtml|phtml|php)$">
                SSLOptions +StdEnvVars
        </FilesMatch>

        <Directory /usr/lib/cgi-bin>
                SSLOptions +StdEnvVars
        </Directory>

    </VirtualHost>
</IfModule>

What should I do to solve this? Thanks.