timeouts (ERR_CONNECTION_RESET) on seemingly random files after upgrading to HTTPS

Question

I have a WordPress site on a managed host (discountasp.net) that has run for several years. A few days ago I upgraded the managed site to use https by installing an SSL certificate (the actual installation was done by discountasp.net). As part of the troubleshooting so far I have upgraded to PHP 7.0 and WordPress 5.6.

Now, when loading any WordPress page, including the admin login page, I get random timeouts on various files. If I look in Chrome dev tools, I see that many files load immediately, but one or more time out.

In the example above, the file is jquery.js, but other files often fail to load also, especially .css files. Note that in the example above, it is the wp-admin page that is failing to load. I have also renamed the wp-content/plugins and wp-content/themes directories, so I don’t believe any plugins or themes are involved here. So I believe all I’m trying to do here is visit the login page for a newly installed WordPress 5.6.

I can’t tell if this is a problem in WordPress or a problem with discountasp.net. So far discountasp.net tech support has not been able to say anything useful. As I say, this site ran for years without trouble until I installed the SSL certificate. And that’s the only change I made, so presumably that’s what’s making these files fail to load, but I don’t understand why.

Also, I did trying adding these lines to wp-config.php.

define('FORCE_SSL_LOGIN', false);