If you have any problems with the server which can’t be addressed through the reporting system, you can email the administrator (or “admin”) of your server directly.
On Mastodon, you can find the public email address of your server admin on the server’s About page. The same page also lists the server’s rules. To find it, go to your server’s website and click on “Learn More”. You don’t need to be logged in. The email address will be listed in the top half of the About page, just above the list of rules. It is worth reading the rule list as it varies from server to server, and it is usually written in plain language that is easy to understand.