https://contactforhelp.com/blog/yahoo-mail-not-loading/

There are multiple reasons due to which Yahoo won’t load. It can be because the website is working slow, server error, misconfiguration in settings. You may be using outdated Yahoo application or browser. Another reason #whyYahoowontload is that it has not been installed properly. First, you should uninstall the application and then reload it. Now, properly install it and login to your account. If you still find #Yahooemailnotloading.